By Massimo Calabresi
April 9, 2015

The Mountain View Inn in Cleveland, Tenn., with its stucco ceilings, track lighting and plastic orchids, is a long way from the $1,500-a-night suites at the Beau-Rivage Palace Hotel in Lausanne, Switzerland, where U.S. and Iranian diplomats struck a provisional nuclear deal on April 2. But five days after that deal was announced, Tennessee Republican Bob Corker, chairman of the Senate Foreign Relations Committee, found himself engaging in a debate in the motel’s restaurant that could, in its own way, determine the shape of the Middle East.

The 40-odd attendees at the Bradley County Republican Party meet-and-greet that rainy April morning were mostly older, well-informed business people, with a few local politicians and retirees mixed in, and their questions were almost all about the Iran deal. Could the Iranians be trusted? Why wasn’t the U.N. doing more? Corker, who had woken at 3:30 that morning to go running so that he could be “fresh” for the day’s meetings with constituents, paced and gesticulated, answering their questions with minute detail about centrifuges, uranium stockpiles and shifting strategic interests.

Then Jane Rumbaugh, the 76-year-old vice president of the Bradley County Republican Women, piped up. Corker had said the Bush and Obama Administrations had developed a “bunker-busting bomb” that could take out the hardest Iranian nuclear targets. “Why can’t we just use the bunker busters and be done with it?” Rumbaugh asked.

The bombs were a last resort, Corker said. If you went to war with Iran, he continued, they’d be certain to try to build a nuclear weapon the next chance they got, destabilizing the region and threatening America’s allies. And setting them back further could require invasion. “Going into Iran would make going into Iraq look like child’s play,” he said. Rumbaugh wasn’t buying it. She still thought the Iranians would learn their lesson if the U.S. just took out their nuclear infrastructure from on high. Shouldering her crocheted stars-and-stripes handbag after the event, she said of the argument that bombing wouldn’t stop Iran, “I don’t believe it.”

For the next 10 weeks or so, Corker is going to be one of the most important people in the world. Since the late 1990s, the West has been trying to ensure that Iran, a persistent backer of terrorists and regional instability, doesn’t get a nuclear weapon. More than anyone else, Corker will determine whether Congress helps or hurts that effort ahead of a June 30 deadline for a final written deal between Tehran and major world powers. Just as crucial, Corker is positioned to be the key arbiter of American support for or opposition to a deal, which may in turn determine whether it actually lasts. Many Republicans, like Rumbaugh, want the U.S. to take a more confrontational approach, while Obama is trying to sell his political framework even before negotiators put into writing the actual details. Corker, who favors diplomacy but won’t sign off on the deal until it’s finalized, has assigned himself the task of moderating an American consensus, one way or the other.

It’s not a role anyone would have imagined for Corker when he arrived in the Senate in 2007. By his own admission, the wiry Senator, who tops out at something close to 5 ft. 6 in. and cheerfully dogs his opponents with a high-speed tenor twang, knew nothing about foreign policy then. A self-made construction millionaire, his claim to political fame was helping turn Chattanooga from a blighted and polluted postindustrial town into a model of urban revitalization.

But Corker fits the mold of many pragmatic Tennessee Senators of the recent past, such as Howard Baker and Jim Sasser: hardworking, politically savvy and, in an era of reflexive partisanship, instinctively collaborative.

That hasn’t always worked out for Corker on Capitol Hill. His early effort to force auto-bailout sacrifices from both unions and carmakers attracted Democrats to the table but failed to win the support of his Republican colleagues, and he would later join them in voting against the final bill. He labored to produce a key bipartisan section of the Dodd-Frank financial-reform package, only to see the bill pass on partisan lines. (He voted against it even though his provisions remained.) And in 2013, he played a key role in getting the Senate’s immigration-reform bill passed, then watched it die in the more ideological GOP-led House.

Those efforts have nevertheless earned him respect from GOP hard-liners and the White House alike. When it comes to the Iran deal, Obama said April 4, Corker “is somebody who is sincerely concerned about this issue and is a good and decent man.” Whether he’s earned lasting allies for the nuclear-deal fight is another matter. The first test for Corker comes April 14, when he moves forward a bill to give Congress a vote on any deal the U.S. ultimately cuts with Iran. Obama has threatened a veto, saying it could make it impossible to get a signed agreement. Some Republicans grouse that Corker’s bill is not tough enough on Tehran and plan on trying to amend it. Not even Corker knows if his bill, or the deal, will survive. With the fate of the Middle East in play, Corker is jittery about how events will unfold. “We’re a little anxious,” he says.

A Voice for Congress

Corker has already played a role in shaping the Iran deal. On Jan. 19, he arrived in Jerusalem with six other Senators on a Middle East mission to see what U.S. allies in the region thought of the talks. Senate Republicans, and some Democrats, were rallying behind a bill that would impose new sanctions on Iran to try to force Tehran to make concessions in the nuclear negotiations. U.S. and Israeli intelligence believed the bill, authored by another moderate Republican, Mark Kirk of Illinois, could blow up the Iran nuclear talks before they had a chance to succeed. Corker agreed with the spooks and had arranged for the head of the Israeli spy service, Mossad, to brief him and his colleagues in hopes of spreading the word about the dangers of Kirk’s bill.

But as Corker arrived at his first appointment, he was informed that Prime Minister Benjamin Netanyahu, who opposed the talks and believes in directly confronting Iran, had canceled the Mossad briefing. Corker, who can be impatient and demanding and was once described by a Chattanooga radio host as “a hothead,” responded by saying he was canceling the rest of his meetings, including one with Netanyahu, and returning to Washington. The trip was salvaged, but only after Ron Dermer, Israel’s ambassador to the U.S., personally intervened with Netanyahu. When the Senators finally received their briefing from the head of Mossad, Tamir Pardo, he told them the bill would be like “throwing a grenade” into the talks. On the plane home, Corker pressed his case for sidelining Kirk’s bill.

The events overseas put the legislative ball squarely in Corker’s court, and he quickly began to dribble. His strategy is complicated but vital to the conduct of foreign policy in a politically divided era: he wants to lay down a specially designed legislative road map for getting Obama’s Iranian deal in front of–and potentially through–Congress. That means letting every side have a chance to be heard without letting a tiny minority shut it down.

He started by dusting off a year-old bill that would have imposed new sanctions on Iran. Tim Kaine, a Virginia Democrat who had been with Corker on the Israel trip and has close ties to the White House, wanted to join forces with Corker. Senior Administration officials, including the President, urged Kaine to oppose the Tennesseean’s efforts. But Kaine thinks Congress should weigh in on the deal sooner rather than later.

The revised bill would require Obama to submit the Iran deal to Congress and would block him from lifting sanctions for 60 days. Congress could then vote to oppose the deal, support it or take no action. Either of the last two options would allow the deal to go ahead.

Though the Administration publicly decried Corker’s bill and has said Obama would veto it, White House officials respect Corker’s effort to play a productive role. In fact, in private, Administration officials concede that his efforts have already helped American negotiators force the Iranians to meet the self-imposed March 31 deadline for an oral agreement.

Not that the Iran deal is done or is even guaranteed to get done. The framework that emerged from Lausanne was sparse in its written version but detailed in what the Administration said it would ultimately be able to deliver. Iran would cut its enriched-uranium stockpile from 10,000 kg to 300 kg. It would take its operating centrifuges from 19,000 installed centrifuges to a little over 6,000.

But it was maddeningly vague on other details. It was not clear when the Americans and their international allies had promised to lift European, U.N. and U.S. sanctions, and the Iranians muddied the waters by claiming they would get immediate and full relief. In the key area of inspections, which are crucial to preventing Iran from secretly pursuing a bomb, the Administration’s talking points didn’t say how intrusive surprise checks of suspicious sites could be, and the White House dodged questions on the subject in the days after the deal.

The reaction to the Lausanne announcement has been mixed. Netanyahu said a deal based on the April 2 framework would “threaten the survival of Israel.” House Speaker John Boehner said it would “pave the way for a nuclear-armed Iran in the near future.” But the Saudis, Iran’s implacable regional foe, said it was a good deal, as did Democrats and most world powers. For their part, Iranian hard-liners appear to be supporting the deal too, issuing statements in praise of the negotiators and tamping down their normally confrontational rhetoric. Even so, in private, White House officials say they’ll believe they have a deal if and when the Iranians actually sign one.

Which is why Corker argues that the threat of a skeptical Congress hanging over the talks between now and the June 30 deadline will once again help negotiators limit Iran’s expectations for what it can get. More important, he says, if the deal ultimately has Congress’s blessing, it is more likely to last. “If we can pass this bill,” Corker told the members of the Kiwanis Club of Maryville later in the day, on April 7, the all-important details “will be stronger, more enforceable, more accountable, more transparent,” and the U.S. “will have a greater chance of ensuring whatever deal is done is one that will stand the test of time.”

Made in Chattanooga

Corker is a product of a narrow stretch of America running from the Blue Ridge Mountains to the Mississippi and bordering eight states along the way. Tennessee split during the Civil War and has remained politically divided ever since. Slammed by the Great Depression, it was one of the biggest beneficiaries of Franklin Delano Roosevelt’s 1933 Tennessee Valley Authority (TVA), which built dams on the Tennessee River to control flooding and generate electricity for the long-struggling part of the country. The result for eastern Tennessee was jobs, power and ultimately new businesses that were drawn by the massive public-works project.

One of those businesses was chemicals giant DuPont, which built a major plant near Chattanooga thanks to the available power of the TVA dams. Corker’s father worked for the company, and in 1963 they were transferred there from South Carolina. The competitive 11-year-old Corker made fast work of fitting in at his new school, pitching a no-hitter in his first baseball game, he says. He went on to be student-council president and played two years of baseball at the University of Tennessee, he says. He also played high school football, even though he weighed only 140 lb., according to his college friend Jimmy Haslam, owner of the Cleveland Browns. “Bob’s a competitive individual,” Haslam says. “If you’re going to beat him, you better be prepared to work for a long time.”

Corker has been punching above his weight ever since. After college, Corker went to work for a construction company, supplementing coat-and-tie office work with field experience laying rebar and pouring cement. He saved $8,000 and started his own company building small shops. He “got into his groove” building drive-throughs for Krystal Burger, a fast-food chain headquartered in Atlanta that was growing rapidly in the 1980s.

If Corker’s business was growing, the city of Chattanooga was a mess. In 1969 it had the dirtiest air in the country–drivers used their headlights in the daytime–and its stretch of the Tennessee River, curving through the heart of the city, was severely polluted. The downtown, which had lost people to the suburbs for years, was beset with crime. By the 1980s it was in “economic and population free-fall,” according to one study.

A few civic leaders were trying to turn the city around, starting with Chattanooga’s riverfront. Corker had been spending weekends repairing houses in poor downtown neighborhoods as part of his church outreach. (Raised a Methodist, he’s now an Episcopalian.) Corker bearded one of the moneymen behind the revitalization movement at lunch one day and pitched the need for more affordable and livable housing. With foundation money behind the idea, Corker was put on the task force that eventually led to housing improvements benefiting 10,000 families.

After a stint as the state’s commissioner of finance and administration in Nashville–essentially its chief operating officer–Corker was recruited back to run for mayor of Chattanooga by its then Democratic mayor Jon Kinsey. By the time he took office in 2001, Chattanooga was well on the way to renewal, but rather than cutting taxes and government spending, Corker doubled down on the tradition of government improvement, imposing a hotel tax, issuing $60 million in new debt and using the money to reroute a Riverfront Parkway and open green space, public arts and new housing on the river’s south shore.

Corker arrived in the Senate in 2007 and, with a mayor’s sensibility, imposed a disciplined system of metrics on staffers to ensure constituent service: all field-and caseworkers have numerical targets for site visits and constituent requests they’re expected to handle each month. On the legislative side, Corker set about learning policy. After the financial crisis he dove into the auto-bailout and Dodd-Frank battles. He was later attacked by some on the left for calling JPMorgan CEO Jamie Dimon “one of the best CEOs in the country.” (Corker dismissed JPMorgan’s more than $6 billion losses from the infamous London Whale as a “blip on the radar screen.”) But Corker was instrumental working with Virginia Democratic Senator Mark Warner on giving the Federal Deposit Insurance Corporation new powers to safely resolve failing financial institutions, a provision that ended up being a major part of Dodd-Frank.

Corker was less successful on the 2013 immigration bill. At the height of the battle over the reform package, Corker played a round of golf with Obama and two other Senators at Joint Base Andrews, outside Washington. He says the game was “a very pleasant social experience” and that he and Obama “didn’t really talk about” immigration. Soon after, however, Corker persuaded Democrats to support a $38 billion amendment to the bill that would have added fencing and agents along the border. The bill ultimately passed but went nowhere in the House. Even so, Corker had established himself as an honest broker. New York Senator Chuck Schumer, likely the next Democratic leader in the Senate and a fierce partisan, called Corker a “reasonable, trustworthy negotiator” whom “Democrats and the White House can have productive discussions with.”

But it is in the overseas arena that Corker has excelled. In 2010 he bucked powerful Senators in his party to support Obama’s New Start Treaty, which cut U.S. and Russian nuclear arsenals. Corker authored one of the amendments that delivered the votes needed for ratification. And since taking control of the Senate Foreign Relations Committee, he has earned consistently high praise from the Obama diplomatic team, though much of that praise has been delivered sotto voce. “He’s independent and doesn’t kowtow to anybody,” says former FDIC Chair Sheila Bair. “It makes me feel good to know he’s going to be one of the people having a close look at the Iran deal.”

Building a Better Deal

Corker’s immediate task is getting a veto-proof 67 votes for his bill after he leads the Foreign Relations Committee vote on it on April 14. Corker has said he’s open to amendments from both sides. Republicans are expected to file some blasting Obama’s deal, while Democrats wanted to make changes to soften Congress’s ability to block it. As for the White House’s supposed opposition, even Kaine says he doesn’t think Obama will ultimately veto the bill.

If it gets past Obama, Corker’s bill will set up a period of tough congressional oversight as negotiators try to reach a final written deal by the deadline of June 30. Corker sees his role as building a broader consensus in America for the U.S.-Iran deal, if the negotiators can deliver it. “We want to go through it on behalf of the American people,” Corker says.

Back home, it seems likely Tennesseeans will follow his lead. At the Maryville Kiwanis Club, many citizens were clearly skeptical of the Iran deal and had chosen for their convocation Matthew 7:15: “Beware of false prophets, which come to you in sheep’s clothing, but inwardly they are ravening wolves.” But they also performed their regular declaration of the club’s global-minded goals: to make the world a better place one child, and one community, at a time. And as one speaker after another got up to thank Corker for his work in Washington, it seemed they trusted him to figure out how to do that.

–WITH REPORTING BY ALEX ALTMAN, ALEX ROGERS AND ZEKE J. MILLER/WASHINGTON

Contact us at editors@time.com.

This appears in the April 20, 2015 issue of TIME.

SPONSORED FINANCIAL CONTENT

Read More From TIME

EDIT POST