(Julie Jacobson | The Associated Press) In this Thursday, Feb. 2, 2012 file photo, Donald Trump greets Republican presidential candidate, former Massachusetts Gov. Mitt Romney, after announcing his endorsement of Romney during a news conference in Las Vegas. Mitt Romney and President Donald Trump exchanged harsh criticisms of one another during the 2016 presidential campaign but also have a history of being willing to sit down with each other when mutually beneficial. Romney's announcement that he's running for the U.S. Senate seat in Utah creates the potential for future battles, or even deal-making.