"His promises are as worthless as a degree from Trump University," Romney will say of Trump. "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."
Romney, the party's nominee in 2012, will urge Americans "to make the right choices" and not support the GOP front-runner during a speech he'll give Thursday at 11:30 a.m. ET at the University of Utah's Hinckley Institute of Politics Forum.
With Dr. Ben Carson bowing out of tonight's Republican presidential debate, Romney will promote the remaining candidates. According to the former Massachusetts governor, "the only serious policy proposals that deal with the broad range of national challenges we confront have come from Ted Cruz, Marco Rubio and John Kasich."
But even as the former Republican standard bearer tries to lead the effort to stop Trump, the belated push may only reinforce the real estate mogul's appeal. Trump supporters have already shown their deep loathing for establishment figures and Romney's rhetorical assault against Trump could ring hollow after his effort in 2012 to win Trump's endorsement.
Romney is expected to remark on some what-ifs about Trump becoming president. "His domestic policies would lead to recession. His foreign policies would make America and the world less safe. He has neither the temperament nor the judgment to be president," Romney is expected to say.
Nightcap: Ben Carson heads for the exit as Mitt Romney takes aim at Donald Trump | Sign up
Romney will also touch on a "twisted example of evil trumping good: "Trump's claims that he admires Russian President Vladimir Putin while calling "George W. Bush a liar."
It is clear that Romney thinks a Trump nomination is troublesome for both the Republican Party and the country.
MORE: Serene Canadian island courts 'Trump refugees'
In the wake of Super Tuesday results, Romney will also address what many are presuming the general election will look like: Hillary Clinton vs. Trump.
Trump fires back
Trump kicked off an anti-Romney social media tirade late Wednesday night, posting a Facebook video accusing the former Massachusetts governor of being soft on cornerstone conservative issues, including immigration and abortion.
Then he lambasted Romney on social media Thursday morning ahead of the speech.
The business mogul, who himself has changed positions on abortion, continued hitting Romney and the Republican establishment Thursday morning in a series of tweets.
"I have brought millions of people into the Republican Party, while the Dems are going down. Establishment wants to kill this movement!" Trump tweeted.
The GOP front-runner also tweeted he is the only GOP candidate capable of beating Hillary Clinton.
"I am the only one who can beat Hillary Clinton. I am not a Mitt Romney, who doesn't know how to win. Hillary wants no part of "Trump"," he tweeted.
Trump noted that Romney had badly sought Trump's backing when he ran in 2012.
"Why did Mitt Romney BEG me for my endorsement four years ago?" he said.
Trump continued his anti-Romney offensive on morning television Thursday, calling Romney's 2012 presidential bid "one of the worst presidential campaigns in history" on MSNBC's "Morning Joe."
"The biggest story in politics isn't Mitt Romney, it's that the GOP is getting millions and millions of people to vote for me," Trump said.
Clinton gets blasted, too
Romney believes that the current GOP frontrunner "relishes any poll that reflects what he thinks of himself." General election polls, however, say "that he will lose to Hillary Clinton."
According to Romney, nominating Trump to represent the Republican Party will only secure Clinton's victory in November.
MORE: Clinton looks ahead after Super Tuesday
Romney deems Clinton "untrustworthy" and "dishonest." He will tout Clinton's performance as secretary of state and argue that she "compromised our national secrets."
The 2012 nominee is not expected to make any other announcements in his speech today. Romney "understand(s) the anger Americans feel today" but hopes that such anger is "transformed into energy directed for good."
INTERACTIVE: Find your presidential match
