Left Mitt Romney speaks during the Republican National Committee's winter meeting aboard the USS Midway Museum in San Diego, Calif. on Jan. 16, 2015. Right Donald Trump waves as he arrives at a caucus night watch party at the Treasure Island Hotel & Casino in Las Vegas on Feb. 23, 2016.
Gregory Bull—AP; Ethan Miller—Getty Images
February 25, 2016 1:31 PM EST

Donald Trump and Mitt Romney engaged in a snarky Twitter spat Thursday after Romney accused Trump of hiding something in his tax returns.

The fight began Wednesday night, when 2012 Republican nominee Romney said of the current GOP frontrunners, “We really ought to see from all three of these fellas what their taxes look like to see if there’s an issue there. I think in Donald Trump’s case, it’s likely to be a bombshell.”

(Romney, a co-founder of private equity company Bain Capital, came under pressure himself during the 2012 race to disclose his tax returns.)

The fight escalated Thursday, when businessman Trump fired off a series of tweets bashing Romney:

Trump also took a moment out of attacking Romney to make a pitch for simplifying the tax code, something he’s talked about on the stump:

But Romney wasn’t cowed by the tweet-storm, and hit back at Trump in kind:

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Write to Tessa Berenson at tessa.berenson@time.com.

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