Mitt Romney told his advisors to look into how to block GOP front-runner Donald TrumpDonald TrumpTrump daughter-in-law joins Trump campaign digital vendor: report Live coverage: Senate intel holds first public Russia hearing Federal judge extends order blocking Trump's revised travel ban MORE at the Republican National Convention, CNN reported Thursday.
"It sounds like the plan is to lock the convention," a source close to Romney's inner circle told CNN.
Romney is reportedly looking to prevent Trump from getting the required 1,237 delegates before the convention for the Republican nominee. He also doesn't think rivals Marco RubioMarco RubioRepublicans giving Univision the cold shoulder: report Week ahead: Senate panel to vote on Trump's Labor pick Senators introduce new Iran sanctions MORE, Ted CruzTed CruzTexas Dem targets Sen. Ted Cruz in 2018 What are 'religious liberty' bills really about? Fiorina calls for special prosecutor for Russia probe MORE or John Kasich will get the required number of delegates before the convention.
Earlier Thursday, Romney bashed Trump in a speech, calling him a "phony" and a "fraud." He urged the public to vote for the candidate that will prevent Trump from getting delegates in their state.
"If the other candidates can find common ground, I believe we can nominate a person who can win the general election and who will represent the values and policies of conservatism," Romney said.