RNC Rules Committee Chairman Bruce Ash listens to a speaker during the Republican National Committee (RNC) Spring Meeting at the Diplomat Resort on April 21, 2016 in Hollywood, Fla.
Joe Raedle—Getty Images
July 15, 2016 8:30 AM EDT

Correction appended, 6:39 p.m.

On the surface, selecting a presidential nominee sounds like a straightforward affair: people head to the polls and vote and, once each state has had its turn with a primary or caucus, delegates are added up. By that point, the parties should have their nominees. But nothing is sure until the nominating conventions that are held the summer before general elections—this year, the Republicans will hold their convention next week in Cleveland and the Democrats will convene July 25 through the 28 in Philadelphia—and each convention has a special committee with the power to change the rules of nomination.

As independent entities not beholden to the constitution or the will of the people, political parties are free to run their conventions as they see fit. For both parties, rules committees are able to alter the rules of the conventions either before or during a convention, and thus have the potential to impact elections in a massive way.

Stan M. Haynes, attorney and author of The First American Political Conventions: Transforming Presidential Nominations (1832-1872), tells TIME that rules committees have been in existence ever since the very first conventions. Until that time, members of congress voted for and decided on their party’s presidential nominees. As this process came under greater and greater scrutiny for not involving a vote of the people, as Haynes writes, it was criticized for being “un-American,” the process slowly changed until conventions were established in 1832.

Though often under the public’s radar, the role of the rules committees would be impossible to understate, as they more or less dictate how presidential nominees are chosen, says Haynes. While the conventions were put in place to allow for the electorate to have more of a voice, there have been a couple of elections where the rules committees altered things such that the parties could choose the candidates they liked best, sometimes with significant consequences.

Haynes points to two specific examples of rules committees having an impact on the nomination—and potentially all of American history.

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The most dramatic case of the rules committee taking over, Haynes says, was in 1844, when Democratic president Martin Van Buren was running for reelection. Many high-ranking people in the party felt that, while he was popular, Van Buren was not the best nominee. The reason why? Van Buren was against the annexation of Texas from Mexico. Party members including Andrew Jackson wrote a letter to the convention hoping to block Van Buren’s nomination, with a view to ending up with a President who favored bringing Texas into the United States.

Usually, under Democratic Party rules, a candidate needed two-thirds of the votes to secure the nomination. But some party members tried to challenge this rule in favor of applying a simple majority rule. However, the rules committee ultimately decided to stick with the two-thirds rule, which created an opening for a challenger, and president Van Buren lost to pro-annexation candidate James Polk.

Haynes speculates that the United States may not have moved to acquire Texas had Van Buren won, which means that the Mexican-American war would not have occurred. The U.S. could have fought to take Texas later, but who can say for sure?

Another significant rules committee decision was on the Republican side in 1880. That year, Ulysses Grant, who Haynes says was the “king of political corruption” at the time, was hoping to make a comeback after two terms and a one-term hiatus. During his presidency, Grant had, among other controversies, been involved with the Whiskey Ring in 1875, a tax diversion scheme involving Washington bigwigs and whiskey makers that landed money in the pockets of politicians.

By the time the 1880 convention rolled around, segments of the party were concerned about the implications of Grant’s corruption for the Republicans. During this period, the Republicans sometimes used a rule known as the unit rule, under which all of a state’s convention votes were cast for the candidate picked by that delegation’s majority.

The convention defeated the use of the unit rule that year, opting to allow each delegate to cast an individual vote, which gave James Garfield the nomination by a small margin. Had the unit rule been applied during that convention, Grant most likely would have been nominated, and would have faced off against Winfield Scott Hancock in the general election. Again, there’s no telling what would have happened, but Garfield won the electoral vote handily against Hancock, and went on to have a tame and uneventful presidency. Any number of other things could have transpired had Grant not been blocked at the convention.

Rules committees came under the spotlight again for 2016, on both sides of the aisle. Before Donald Trump secured the number of popular votes needed to become his party’s presumptive nominee, many prominent members of the Republican party said that they did not want him in that position—leading some speculate that the RNC could have blocked Trump by tossing out a rule that candidates must win eight states during the primaries in order to be eligible. That would have meant that any number of candidates could be considered for nomination under a brokered convention. As for the Democratic National Convention, Senator Bernie Sanders’ campaign wrote a letter to the DNC on May 28 petitioning for the removal of a co-chairs of the convention’s rules committee, former Representative Barney Frank, calling him one of the party’s “aggressive attack surrogates for the Clinton campaign.”

Though the primary process was such that this year’s conventions seem unlikely to provide opportunities for the rules committees to make an impact, the campaign served to draw attention to the committees and the power they wield. As all eyes turn to Cleveland and Philadelphia, that fact is worth remembering.

Correction: The original version of this article misstated which rules were used at nominating conventions in 1844 and 1880. The Democratic Party in 1844 used the two-thirds rule; the Republican Party in 1880 rejected the unit rule.

Contact us at editors@time.com.

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