Mitt Romney, the 2012 Republican presidential nominee, said he would support an effort to deny Donald Trump the nomination at the party’s convention in July if Trump doesn’t have enough delegates to win on the first ballot.

"A person like Donald Trump, who has said what he’s said about Muslims, Mexicans, women, George Bush, John McCain, a person like that should not be the nominee of our party or be the president, and I will campaign for an alternative to Donald Trump until that avenue is no longer open," Romney told Mark Halperin in an interview for Bloomberg Television’s "With All Due Respect."

Romney also said he might contribute to super-PAC efforts attempting to block Trump from getting the nomination.

“I may. That’s something my wife and I will have to decide,” he said.

But as Trump and Clinton continue to pull ahead in delegate counts, the former Republican nominee compared the choice between the two as "drink the poison or take the bullet.”

“If those are my only two choices I’d vote for a conservative on the ballot -- and if there weren’t one that I was comfortable with, I would write in a name,” he said.

“I think there will be a lot of people who would be very troubled with those choices,” Romney said.

Some Republican leaders, despairing about Trump’s dominating performance on Super Tuesday, are becoming increasingly convinced that the only viable way to stop the front-runner is for his rivals prevent him from getting the 1,237 delegates needed to clinch the nomination. That scenario would prompt a rare contested convention where, the theory goes, an alternative could be crowned the nominee if Trump is unable to win a majority of delegates.

Asked whether he would accept the nomination in the face of a draft-Romney movement backed by a majority of delegates at the convention, Romney said he “isn’t going to go there,” and isn’t interested in being the nominee.

"The reality is that our nominee will most likely be Donald Trump, unfortunately, and if I’m successful and the other candidates are successful, then it’ll be one of the other people running for president," Romney said. "But it’s not going to be someone who’s not running for president, not seeking that office, doesn’t have the staff to help organize that effort, to whip the delegates into supporting them. That’s not what I’m doing."

Romney said "nobody is entitled to the nomination," not even a candidate with a plurality of delegates heading into the convention. "The voters of the country decide who they want to support, and the delegates are elected to also make a determination of who would be in the best interest of the party and the country to be our nominee."

"Either you’ve got to get the delegates and show that you have the support of the nation and you’ve got the 1,237 delegates, and if you didn’t then you’ve got to go to the convention and convince the delegates," he said.

Romney has become the leading establishment voice to stop Trump from getting the Republican nomination, and gave a speech Thursday where he said Trump is not fit to be president, because of his vulgar personal ways and lack of depth and knowledge about foreign and domestic matters. Trump replied by saying the Romney was a "failed candidate" who embarrassed the party with such a poor showing against President Barack Obama, who beat Romney handily in 2012.

Before the speech, Romney had stepped up criticism of Trump for the billionaire’s delay in releasing his tax returns, suggesting they may contain a "bombshell." Romney, the chairman of Solamere Capital LLC in Lexington, Massachusetts, himself came under pressure as a candidate over his tax returns.

"I think everyone has the same evidence I do, which is he does not want to release his tax returns under any circumstances," Romney said in the interview. "I don’t believe he ever will because there’s something in there that he’s afraid that if the people saw it they wouldn’t vote for him for the nominee."

Romney said he’ll continue to make the media rounds, including on a Sunday talk show or two.

"I’m doing this, and that probably reaches more voters than actually showing up in a state and I’m not sure that my showing up in a state would make much difference anyway," he said. "Most people want you to come in and endorse a candidate but I’m not doing that."

(An earlier version of this story incorrectly stated the year Obama beat Romney.)

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