The former Massachusetts governor and the 2016 Republican presidential front-runner have gone from laying out compliments to slinging criticisms now that the tables have turned.
What Trump Said Back Then
Trump, back when he was just a real estate mogul and reality-TV star without adding candidate to his list of titles, endorsed GOP nominee Romney for the 2012 election and praised his business savvy, calling it an "honor" to endorse him for president.
"Mitt is tough, he is smart, he is sharp, he is not going to allow bad things to continue to happen to this country we all love. So Governor Romney, go out and get 'em!" Trump said.
Now, Trump has turned to Twitter to slam Romney.
How Romney's Reaction Has Changed
For Romney's part, an early preview of the remarks he is set to give in a speech today shows that he is planning to call Trump "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," Romney is expected to say.
That strikes a clear contrast to the pleasantries that Romney shared when the billionaire endorsed him four years ago, calling Trump's support "a delight."
"Donald Trump has shown an extraordinary ability to show how our economy works. To create jobs for the American people. He has done it here in Nevada, he has done it across the country. He understands that our economy is facing threats from abroad," Romney said during the 2012 endorsement.
While the full extent of Romney's speech won't be revealed until he addresses the Hinckley Institute of Politics at the University of Utah at 9:30 a.m. local time, Romney's former running mate weighed in on the possible reason behind Romney's speech.