Ann Romney looks on as Donald Trump and Republican presidential candidate Mitt Romney shake hands during a news conference held by Trump to endorse Mitt Romney for president at the Trump International Hotel & Tower Las Vegas on Feb. 2, 2012 in Las Vegas, Nevada. (Photo by Ethan Miller/Getty Images)

NEW YORK (CBSNewYork) — Donald Trump is firing back at Mitt Romney after the former Republican presidential nominee said there could be a “bombshell” revelation in Trump’s tax returns.

Trump took to Twitter, saying the former Massachusetts governor is trying to play a “tough guy.”

“Mitt Romney, who totally blew an election that should have been won and whose tax returns made him look like a fool, is now playing tough guy,” the GOP hopeful tweeted.

Mitt Romney,who totally blew an election that should have been won and whose tax returns made him look like a fool, is now playing tough guy — Donald J. Trump (@realDonaldTrump) February 24, 2016

Trump also called Romney “awkward and goofy.”

“When Mitt Romney asked me for my endorsement last time around, he was so awkward and goofy that we all should have known he could not win!” Trump said.

When Mitt Romney asked me for my endorsement last time around, he was so awkward and goofy that we all should have known he could not win! — Donald J. Trump (@realDonaldTrump) February 24, 2016

In an interview with Fox News earlier Wednesday, Romney insinuated a possible “bombshell” in Trump’s tax returns.

“I think there’s something there. Either he’s not anywhere near as wealthy as he is, or he hasn’t been paying the kind of taxes we would expect him to pay,” Romney said.

He continued, “The reason I think there’s a bombshell in there is because every time he’s asked about his taxes, he dodges and delays and says, ‘Well, we’re working on it.’ Hey, we’re not talking about the taxes that are coming due this year … We’re talking about taxes that already filed.”

Romney touched on his tax return issue in 2012 when President Barack Obama’s campaign forced him to release five additional years of his tax returns.

“We’re going to select our nominee. We really ought to see from all three of these fellows what their taxes look like to see if there’s an issue,” Romney told Fox News. “I think in Donald Trump’s case, it’s likely to be a bombshell.”

Just four years ago, Trump called Romney “tough,” “sharp,” and “smart” in his endorsement.

“He’s not going to allow bad things to continue to happen to this country that we all love,” Trump said in 2012 when he endorsed Romney for president.

Trump is on a roll heading into next week’s Super Tuesday. The billionaire secured a third straight victory in his bid to become the Republican presidential nominee after capturing the Nevada GOP Caucus Tuesday.