Mitt Romney is letting Donald Trump know what he really thinks.

The Republican presidential nominee in 2012 is expected to call the GOP presidential front-runner in 2016 a “phony and a fraud.” The remarks are the strongest by the Republican establishment, and an apparent attempt to slow Trump’s momentum, after his sweeping victories on Super Tuesday in which he won seven states and put himself on a course to secure the party’s nomination.

Romney had been teasing his sentiments about Trump on Twitter for days, calling on the billionaire to first release his tax returns and then repudiating Trump’s non-answer on support from a KKK leader. Excerpts from a speech Romney is scheduled to deliver later Thursday were obtained by Bloomberg News.

Romney went on to criticize Hillary Clinton, the presidential front-runner on the Democratic side, saying her policies while secretary of state “diminished” U.S. interests “in every corner of the world.” Yet, he pointed out, “Trump relishes any poll that reflects what he thinks of himself. But polls are also saying he will lose to Hillary Clinton.”  

From the excerpts released Thursday morning it’s unclear if Romney is urging Republicans to vote for anyone other than Trump because Clinton, in his view, is far too dangerous to be president; nor is it clear if he will ultimately decline to vote for Trump if the front-runner secures the Republican nomination.

“A person so untrustworthy and dishonest as Hillary Clinton must not become president,” Romney is expected to say. “But a Trump nomination enables her victory.”

Trump responded almost immediately.

He then went on NBC’s Today show to amplify those views:

The relationship between the two men is complicated. BuzzFeed’s McKay Coppins chronicled in 2012 Romney’s tortured attempt, during his presidential campaign, to win the support of the Republican base, which, in his campaign’s view, ran through Trump.

When the campaign decided to go for it, they went all out. Staffers and surrogates lobbied their contacts in Trump’s office, and senior campaign strategist Stuart Stevens called a person close to the Celebrity Apprentice star and asked what they could do to win him over.

The friend’s advice: “Flattery goes a long way with Mr. Trump.”

And so, in September 2011, the candidate himself paid a visit to Trump Towers in New York City. Other GOP contenders had already made the journey to kiss The Donald’s ring — including Herman Cain, Michele Bachmann, and Rick Perry — but Romney was considered the most serious candidate at that point. Rather than hold a big press conference outside the building like others did, Romney slipped in and out of a back door, dodging the photographers lurking nearby.

No one knows what was said behind those closed doors — only Romney and Trump were present — but whatever it was, the candidate had “charmed” him, according to a source who spoke to Trump afterward. The source added that Trump had seriously considered backing Perry, but Romney’s meeting put him over the edge.

“I think it’s a rich-guy thing,” Trump’s friend told BuzzFeed.

Romney remarks are scheduled for 11:30 a.m. ET at the University of Utah.