Mitt Romney, former Republican presidential candidate and Massachusetts governor, isn’t a Donald Trump fan. In a devastating speech in Utah he made that clear, calling the Republican presidential front-runner a “phony, a fraud” and that dishonesty is “Trump’s hallmark.”

“His promises are as worthless as a degree from Trump University,” Romney said. “He’s playing the American public for suckers: He gets a free ride to the White House and all we get is a lousy hat.”

The stinging rebuke comes on the heels of Trump’s massive success during the Super Tuesday primaries. He’s received endorsements from some prominent Republicans, including NJ Governor Chris Christie and Maine Governor Paul LePage and Alabama Senator Jeff Sessions.

Romney is the latest — and perhaps the most prominent– Republican to declare Trump unfit for office. A growing number of Republicans — some currently in office–are openly declaring that not only do they oppose Trump, but will not vote for him even if he gains the party’s nomination. A few vow to sit out the election, while others say they will back a third party candidate — or maybe even vote for Hillary Clinton, should she become the Democratic nominee. Romney didn’t say whom he’d support if Trump wins the nomination — but he made clear that he believes a Trump presidency would be an utter disaster.

All of the Republicans who have gone public with their opposition cite their principles and conscience as the reason, although it likely doesn’t hurt that some recent polls show either Bernie Sanders or Hillary Clinton would easily beat Trump in the general election.

So far, the heavyweights, such as House Speaker Paul Ryan, have criticized Trump, but have indicated they would support him should he win the nomination. But Marco Rubio, who is seeking the Republican nomination, began using the hashtag #NeverTrump, which was remarkable; as New York Magazine notes, it is “very, very rare for major presidential candidates who lose nomination contests to refuse to endorse the winner.”

Although even if all of the GOP leaders did oppose Trump, it’s not clear it would make a dent in Trump’s popularity. As the Washington Post noted, it seems that the more the Republican elite oppose Trump, the more support he gets from voters.

Below 13 other prominent Republicans who have stated unequivocally they will not vote for Trump. Fortune has reached out to Donald Trump’s campaign for a comment and will update this post if and when we get a response.

Charlie Baker

Background: Governor of Massachusetts.
Statement: In answering a question from reporters after the Tuesday primaries as to whether he would vote for Trump if nominated, Baker said, “I said that I wasn’t going to vote for Donald Trump yesterday and I didn’t and I don’t plan to vote for him in November, but I’m not willing to concede with 35 states still to go that he’s going to be the Republican nominee.”

Baker's First Months Win High Marks
Massachusetts Governor Charlie Baker (Photo by John Blanding/The Boston Globe via Getty Images)Boston Globe Boston Globe via Getty Images

Eliot Cohen

Eliot Cohen, Historiker, USAPhotograph by Minehan — ullstein bild ullstein bild via Getty Images

Background: Influential neoconservative who held multiple positions in the George W. Bush administration.
Statement: In tweeting his “short list” of reasons to not vote for Trump, he listed, “demagoguery, torture, bigotry, misogyny, isolationism, violence. Not the Party of Lincoln & not me.”

Carlos Curbelo

Carlos CurbeloPhotograph by Tom Williams — CQ-Roll Call,Inc./Getty Images

Background: Congressional representative from Florida’s 26th district.
Statement: “This man does things and says things that I teach my six- and three-year-olds not to say,” Curbelo told the Wall Street Journal in an interview. “I could never look them in the eye and tell them that I support someone so crass and insulting and offensive to lead the greatest nation in the world.”

Kevin Madden

Kevin Madden with RomneyKevin Madden with GOP presidential nominee Mitt Romney.Photograph by Justin Sullivan — Getty Images

Background: Communications strategist to three Republican presidential campaigns as well as one-time press secretary to former Speaker of the House John Boehner.
Statement: “For many Republicans, Trump is more than just a political choice,” Madden told the Washington Post. “It’s a litmus test for character. I’m prepared to write somebody in so that I have a clear conscience.”

Mel Martinez

Mel MartinezPhotograph by Susana Gonzalez — Bloomberg Bloomberg via Getty Images

Background: Former congressman from Florida and past Republican National Committee chair.
Statement: “I would not vote for Trump, clearly,” Martinez told the Wall Street Journal. “If there is any, any, any other choice, a living, breathing person with a pulse, I would be there.”

Ron Paul

Background: Former presidential candidate and member of Congress
Statement: On Twitter in September, Pataki called Trump “unfit to be president” and said that he wouldn’t vote for him.

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Reid Ribble

Background: U.S. Representative from Wisconsin’s 8th congressional district.
Statement: “I am not obligated to support a bad candidate from any party,” Ribble told the Milwaukee Journal Sentinel. “I will not support Donald Trump for president of the United States, no matter what the circumstances.”

Representative Reid Ribble, a Republican from Wisconsin, speaks at the American Road and Transportation Builders Association's Federal Issues Program and Transportation Construction Coalition Fly-In event in Washington, D.C., U.S., on Tuesday, April 14, 2015. Pressure is mounting for Congress to identify a long-term funding mechanism for highway and mass transit programs ahead of a May 31 deadline. Photographer: Pete Marovich/Bloomberg *** Local Caption *** Reid Ribble
Representative Reid Ribble, a Republican from Wisconsin, Photographer: Pete Marovich/Bloomberg

Tom Ridge

Background: Former Homeland Security Secretary and governor of Pennsylvania.
Statement: When asked on MSNBC if he would vote for Trump should he become the nominee, Ridge said, “Not a chance. I think he’s an embarrassment to the Party, I think he’s an embarrassment to the country.”

Tom Ridge
Former governor of Pennsylvania Tom Ridge (Photo by Alex Wong/Getty Images)

E. Scott Rigell

Rep. Scott RigellPhotograph by Bill Clark — CQ-Roll Call,Inc./Getty Images

Background:Representative of Virginia’s 2nd Congressional District.
Statement:”Trump is a bully, unworthy of our nomination,” Rigell wrote in an email, published by the website Hot Air. “My love for our country eclipses my loyalty to our party, and to live with a clear conscience I will not support a nominee so lacking in the judgment, temperament and character needed to be our nation’s commander-in-chief. Accordingly, if left with no alternative, I will not support Trump in the general election should he become our Republican nominee.”

Ben Sasse

Sen. Ben SassePhotograph by Bill Clark — CQ-Roll Call,Inc./Getty Images

Background: Republican Senator from Nebraska
Statement: “A presidential candidate who boasts about what he’ll do during his ‘reign’ and refuses to condemn the KKK cannot lead a conservative movement in America,” Sasse wrote on his Facebook account. On Twitter he said, “If Trump becomes the Republican nominee my expectation is that I’ll look for some 3rd candidate – a conservative option, a Constitutionalist.”

J.C. Watts

The Second Chance ActPhotograph by Tom Williams — CQ-Roll Call,Inc./Getty Images

Background: Former Oklahoma representative
Statement: Watts told the Wall Street Journal that he would write in a candidate before voting for Trump. “It’s going to be a tremendous setback for the party if he wins,” he said.

Peter Wehner

Peter Wehner, director of the White House Office of StrategiPhotograph by Preston Keres — The Washington Post Washington Post/Getty Images

Background: Served in the administrations of Ronald Reagan, George H.W. Bush, and George W. Bush as a speechwriter and advisor.
Statement: “Mr. Trump’s virulent combination of ignorance, emotional instability, demagogy, solipsism and vindictiveness would do more than result in a failed presidency; it could very well lead to national catastrophe,” he wrote in the New York Times. “The prospect of Donald Trump as commander in chief should send a chill down the spine of every American.”

Christie Todd Whitman

Christine Todd WhitmanPhotograph by Aaron Davidson — Getty Images

Background: Former governor of New Jersey
Statement: “No, I won’t. I can’t,” Whitman said on Bloomberg Politics when asked if she would support Trump should he be nominated. “The kind of rhetoric in which he is engaged, the divisiveness he is encouraging, the belittling of people just by reason of their ethnicity, he is creating a divide in this country that I think is very dangerous for the future and while I certainly don’t want four more years of another Clinton administration or more years of the Obama administration, I would take that over the kind of damage that I think that Donald Trump could do to this country, to its reputation, to the people of this country.”