The rapidly intensifying effort by the Republican establishment to dislodge Donald Trump from the top of the party's presidential nominating race will star 2012 nominee Mitt Romney, who is preparing a speech for Thursday when he'll lay out his case against the front-runner.

With Trump's convincing victories on Tuesday, the single biggest day of voting in the Republican race, Romney was motivated to make a more formal case against him in hopes of keeping him from coalescing more support, according to a Republican source familiar with Romney's plans. Romney has voiced criticism for Trump in recent months, including his attack last week on the New York businessman's refusal to release his tax returns. 

Romney doesn't believe Trump is the right person to lead the party, the Republican source said. A number of mainstream Republicans are falling in line with Trump, and Romney wants to speak up before more people go that route, the source said.

While making the case against Trump at the Hinckley Institute of Politics Student Forum at the University of Utah, Romney will not endorse one of his opponents, two people familiar with the former Massachusetts governor's plans said. Romney will, however, praise Florida Senator Marco Rubio, Texas Senator Ted Cruz, and Ohio Governor John Kasich. Romney’s comments will be focused on “the state of the race,” likely echoing past criticism of Trump for failing to release his tax returns, and not decisively distancing himself from the Ku Klux Klan.

Closing Window

Romney's attempt to shape the race comes after 15 states have held nominating contests. Trump has won 10 of those contests, and has 46 percent of the delegates awarded so far.

Trump has also collected endorsements by New Jersey Governor Chris Christie, a leader of the party who once served as head of the Republican Governors Association, Maine Governor Paul LePage, and U.S. Senator Jeff Sessions of Alabama.

The battle inside the GOP is so fluid that Romney's circle of advisers are not in agreement about how to respond to Trump's rise towards the nomination. 

“There are Republicans opposing Trump, but they are a tiny minority when you look at the voting,” Eric Fehrnstrom, a Republican consultant who was a senior adviser to Romney's campaign, said in an interview. “The party leadership could make more progress if they focused on building bridges instead of burning them.”

Fehrnstrom noted that Romney won six of 10 contests on Super Tuesday four years ago. In the Super Tuesday contests that took place this week, Trump won seven of 11 states.

“What usually happens right now is the party rallies behind the presumptive nominee,” Fehrnstrom said. “I suspect that will happen, but it looks like the process will take itself a bit longer to work out.”

Republican strategist Alex Castellanos is urging the party to line up behind the front-runner. 

"Donald Trump whipped the establishment and it is too late for the limp GOP establishment to ask their mommy to step in and rewrite the rules because they were humiliated for their impotence," Castellanos said in an e-mail to the Washington Post on Wednesday. "If Trump is going to be our nominee, as I believe he is, it is our mission to support Trump and make him the best nominee and president possible."

Beating Trump in Florida

Ahead of Romney's speech, a pair of conservative groups were spending millions on TV ads that hammered Trump, including spots that targeted Michigan, which holds its primary on March 8, and Florida and Illinois, two of the biggest prizes in the race, both of which hold contests on March 15.

The ad campaign effort was focused mostly on the troubled Trump University, which the New York businessman is defending against a pair of fraud claims in his home state.

One 60-second ad from Our Principles PAC, a super-PAC that can take donations in unlimited amounts, contends Trump's real estate school was a “scam” calling it unlicensed, illegal, and offering no actual degrees. The spots are backed by a “seven-figure” ad buy, and will air in Florida, Illinois, Michigan, and on national cable, said Tim Miller, a spokesman for the group.

“The truth about Trump University? Donald Trump made millions, while hard-working Americans got scammed,” the ad says. “Donald Trump belongs in 3 a.m. infomercials, not here.”

A second super-PAC, known as America's Future Fund, is airing multiple spots that feature people they identify as “victims” of Trump University. The spots are part of a $3 million by and running nationally.

“I was duped by the Donald,” a man identified as Bob says in one spot.

Scene in Congress

Word of Romney's speech came as the Republican Party wrestled Wednesday with whether to rally behind Trump or pursue a bloody fight to take him down, with no clear alternative to replace him.

At least some in the party began showing a willingness to get behind Trump after his big night. Senator Ron Johnson of Wisconsin, who faces an uphill run for reelection in a state won twice by Barack Obama, said Wednesday he sees Trump's appeal to voters.

Johnson, like Trump, left a lucrative life in business for politics in a bid to shake up Washington.

“I'll accentuate the positive of anybody,” he said. “I'll look for areas of agreement. Certainly, I would assume a businessperson like Donald Trump can understand a financial statement, understand what needs to be done. I like the fact that he knows how to negotiate. We've had seven, eight years of somebody who doesn't know how to negotiate. I mean that's one of his appeals.”

Elsewhere, Republicans dug in. Neither Rubio nor Cruz, who was buoyed by a home-state victory on Super Tuesday, showed any readiness to make way for the billionaire.

It could spell a brutal war of attrition stretching well into the spring.

Many party stalwarts are loath to back Cruz, an unpopular senator who forced a federal government shutdown in 2013 and then irritated leaders by threatening to do it again. But even some of them began publicly entertaining the idea as Trump’s Super Tuesday rout became clear.

“Ted Cruz is not my favorite by any means,” Senator Lindsey Graham, a South Carolina Republican, told CBS Tuesday night. “But we may be in a position where we have to rally around Ted Cruz as the only way to stop Donald Trump.”

Others in party seemed resigned to Trump, or whatever outcome the party's voters preferred. 

“I'm not worried about what's happening now,” Texas Senator John Cornyn, second-ranking Republicans in the Senate, told reporters, saying the party would eventually unite behind the nominee.

Cornyn also said it was up to senators to speak for or any against any particular candidate. “I'm flattered that you think that voters really care what senators think,” Cornyn said. “My impression is that voters are voting their own minds and they're not looking for guidance or direction from me or anyone else.”

Anti-Trump Playbook

The conservative Our Principles PAC also said it would hire new opposition researchers to examine the real estate mogul’s past. The group on Tuesday night unveiled a YouTube clip featuring several television personalities decrying Trump as a racist. Among the new hires is Miller, the communications director to Jeb Bush’s shuttered presidential campaign.

“Donald’s general election campaign will fail worse than Trump Mortgage and Trump Steaks did and Hillary Clinton will destroy him even if she’s campaigning from jail,” Miller said in a statement, vowing the group would “fight until the last delegate is counted to stop that from happening.”

Trump’s competitors also pitched themselves as the last, best alternative to preventing Trump from earning the nomination—while encouraging each other to exit the race.

“So long as the field remains divided, Donald Trump’s path to the nomination remains more likely,” Cruz said during a victory rally at the Redneck Country Club in Stafford, Texas. “And that would be a disaster for Republicans, for conservatives and for the nation.”

Paired with an emerging Democratic playbook—to accuse Trump of being anti-woman, intolerant, and too hotheaded to have his finger on the nuclear button—it would be the first concerted effort to convince voters that Trump isn’t fit to be president.

Democrats in Washington see opportunity in the Republican melee.

“Most Republicans that are on the ballot, if they share the ballot with Mr. Trump, probably won't see their prospects enhanced,” White House spokesman Josh Earnest said Wednesday. Trump's rhetoric “is directly contrary to the values this country has long defended,” he said, which made him “bullish about the Democrats’ prospects.”

—With assistance from Mark Niquette, Kathleen Hunter, John McCormick, Ben Brody, Steven T. Dennis, Jim Rowley, and Angela Greiling Keane.

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