SALT LAKE CITY — Mitt Romney is expected to make his strongest pitch yet to topple Donald Trump as the Republican Party's presidential front-runner in a high-profile address at the University of Utah Thursday.

But an endorsement in the race is not anticipated from Romney, leaving open the possibility that the GOP could turn to him at the party's national convention in July if no candidate has enough delegates to secure the nomination.

In the address, added to the U. Hinckley Institute of Politics schedule late Wednesday morning, Romney will speak about "the state of the 2016 presidential race."

NBC national correspondent Peter Alexander tweeted out three excerpts from the address this morning.

"Here's what I know," the excerpt reads. "Donald Trump is a phony, a fraud. His promises are as worthless as a degree from Trump University. 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 two-time candidate for the White House, who won the GOP nomination in 2012 but lost to President Barack Obama, has already been confronting Trump in interviews and through social media.

But the billionaire business mogul and reality TV star, who has made statements seen as critical of Muslims, women, immigrants in the country illegally and many others, won big in Tuesday's primaries.

Romney's speech, using his status as an elder statesman in the GOP, may make the most direct case yet to galvanize growing party establishment opposition to Trump as the nominee, a source told the Deseret News.

"Mitt Romney loves his party. He loves his country," longtime supporter Kirk Jowers said. "He is going to take the opportunity to provide his unique perspective on the state of this presidential race and its implications, depending on how it turns out."

Jason Perry, head of the Hinckley Institute, said Romney has not provided details about his address but made it clear he wanted to deliver it in front of an audience of students.

The event will be held at Libby Gardner Hall in the David Gardner Hall Building, 1375 E. Presidents Circle, at 9:30 a.m. Thursday. Seating is limited and will be available on a first-come, first-served basis.

"He's going to talk very directly about this election. He hasn't indicated to us he’s going to be critical of anyone," Perry said. "I haven’t heard he plans on endorsing anyone or making an announcement necessarily about his plans."

There is plenty of national speculation about what Romney will say, with conservative Washington Post columnist Jennifer Rubin suggesting he's "positioned to deliver some tough love" to Republicans.

And, Rubin writes, because Romney was endorsed by Trump in 2012, "he is uniquely positioned to do a mea culpa and tell Republicans that they are in good company if they failed to recognize Trump’s danger earlier."

University of New Hampshire political science professor Dante Scala said he isn't sure how much impact Romney will have on the electorate unless he pushes harder against Trump than most Republican leaders have been willing to do.

"I think Romney does speak from a certain moral strength. They see him as a straight shooter" and he could reach Republicans, Scala said, "if he was willing to say, 'As a matter of conscience, I can't vote for him.'"

Chris Karpowitz, co-director of Brigham Young University's Center for the Study of Elections and Democracy, also said it will be difficult for Romney's message to get traction.

"Here in Utah, he will have a very receptive audience. But he's making his speech in the middle of a raucous, contentious campaign season. It’s not clear to me, unless he says something dramatic, it will."

Karpowitz also said if Romney doesn't endorse one of the other GOP candidates still in the race — Florida Sen. Marco Rubio, Texas Sen. Ted Cruz or Ohio Gov. John Kasich — it's not clear what he'll accomplish.

"I’m not sure that furthers the cause of getting the Republican establishment behind a single candidate unless he’s going to announce," Karpowitz said, suggesting Romney may not be endorsing "to preserve the prospect" of jumping into the race.

Romney has said repeatedly he won't run a third time, but that hasn't stopped speculation he might make a late entry into the primary elections or take advantage of a fractured Republican Party national convention in July.

Jowers told KSL Newsradio's Doug Wright Wednesday that he's been getting "dozens" of calls from former donors and Romney supporters asking when Romney will get involved as a candidate.

"The odds are so low, but they keep improving," Jowers said, adding that Romney's chance for a presidential run would be in a brokered convention, where candidates are "drafted in to save the party."

"Even though Mitt has fantastic approval ratings, that's more regular Republicans and independents who love Mitt," he said. "I'm not sure what Trump's voters would say about it."

Jowers that "it's obviously a fascinating place for someone like Gov. Romney to be, who was such a prominent player in both the 2008 and 2012 elections, to watch this 2016 car wreck."

He said he won't "steal Romney's thunder," but said Thursday's address "will be fascinating and worth listening to."

Not all Republicans are anxious to listen to concerns about Trump.

House Speaker Greg Hughes, R-Draper, said he's supporting Rubio but could back Trump if he becomes the GOP nominee.

"I’d like to see Marco secure the nomination. That said, I’m not interested in attacking the other candidates who are running," the speaker said, urging Republicans not to ignore Trump's political successes.

Utah GOP Chairman James Evans echoed that concern.

Evans said he hopes Romney focuses more on "a better plan for fighting for average Americans than on Donald Trump because that's the only way, the only way, a Republican is going to win in 2016."

Contributing: Wendy Leonard

Email: wleonard@deseretnews.com

Twitter: wendyleonards