Former Republican U.S. presidential nominee Mitt Romney pauses and smiles as he delivers a speech criticizing current Republican presidential candidate Donald Trump at the Hinckley Institute of Politics at the University of Utah in Salt Lake City, Utah, March 3, 2016. REUTERS/Jim Urquhart

UPDATE: 11:42 a.m. EST — Mitt Romney implored Republican voters to vote for anyone but Donald Trump in a speech Thursday, days after the GOP presidential front-runner picked up a majority of votes in Super Tuesday elections across the nation. Romney called Trump a childlish liar who would hurt the Republican brand and help Democrat Hillary Clinton become president.

“Donald Trump says he admires Vladimir Putin, while has called George W. Bush a liar,” Romney said in a speech on the 2016 campaign at the University of Utah. “That is a twisted example of evil trumping good.”

Romney went on the offensive against Trump repeatedly during the speech, saying that the Republican front-runner would be bad for American workers, American families, for the future of the GOP and for the U.S. at large and thanking those who call Trump a "con man and a fake."

Former Republican U.S. presidential nominee Mitt Romney speaks critically about current Republican presidential candidate Donald Trump and the state of the 2016 Republican presidential campaign during a speech at the Hinckley Institute of Politics at the University of Utah in Salt Lake City, March 3, 2015. REUTERS/Jim Urquhart

"If we Republicans choose Donald Trump, the prospects for a safe and prosperous future are greatly diminished," Romney said. He railed against Trump on a wide range of topics, including his healthcare and tax plans and, perhaps most importantly, his business acumen.

“A business genius he is not,” Romney said, rattling off a list of the billionaire's failed business ventures, including Trump steaks and Trump airlines.

Original story:

Mitt Romney is expected to attack Donald Trump and Hillary Clinton during a highly anticipated speech Thursday, while throwing his support behind establishment Republicans Sen. Ted Cruz, Sen. Marco Rubio and Gov. John Kasich. The speech on the state of the 2016 presidential race, to take place at the University of Utah in Salt Lake City at 11:30 EST, will cover topics like North Korea, Russia, China and the future of the Republican Party, according to excerpts of the speech obtained by NBC News.

Along with describing Trump as a “phony" and a “fraud,” the 2012 GOP presidential candidate will tell viewers that the New York businessman is "playing the American public for suckers."

"Donald Trump says he admires Vladimir Putin, while has called George W. Bush a liar," Romney will tell the audience. "His domestic policies would lead to recession. His foreign policies would make America and the world less safe."

Despite accepting Trump’s endorsement for his own run for the White House four years ago, the former Massachusetts governor will explain that a victory for Trump will have "profound consequences" for the country, using rhetoric from a 1964 address by former President Ronald Reagan.

Before declaring last year that he would not run for president in the 2016 race, Romney had favorability ratings of around 27 percent with the general public and 52 percent with Republicans. His speech Thursday will be aimed at traditional conservatives, evangelical and Tea Party supporters that backed him four years ago in an attempt to push them toward establishment candidates rather then Trump, who has attracted many disenfranchised voters but is slowly grabbing more of the traditional Republican base.

Predictably, Donald Trump responded to news of Romney’s upcoming speech on Twitter and during a live broadcast of NBC's "Today" show Thursday morning.

"He begged me four years ago for my endorsement. He's a failed candidate," Trump told "Today" when asked if he thought the speech would have an impact. "Mitt Romney is a stiff," he said, in his trademark name-calling style.

Romney will also pull no punches for Clinton -- he will claim the former secretary of state has compromised national security with her use of personal email for government business and her actions regarding the deadly 2010 raid on the U.S. embassy in Libya. "A person so untrustworthy and dishonest as Hillary Clinton must not become president. But a Trump nomination enables her victory," Romney will say.

International Business Times Tim Marcin contributed to this report.