Sen. Mitt Romney Willard (Mitt) Mitt RomneyCrenshaw looms large as Democrats look to flip Texas House seat The Hill's Morning Report - Sponsored by Facebook - Republicans lawmakers rebuke Trump on election Trump dumbfounds GOP with latest unforced error MORE (R-Utah) said Republicans tend not to publicly criticize President Trump Donald John TrumpFederal prosecutor speaks out, says Barr 'has brought shame' on Justice Dept. Former Pence aide: White House staffers discussed Trump refusing to leave office Progressive group buys domain name of Trump's No. 1 Supreme Court pick MORE because they fear doing so will help Sen. Elizabeth Warren Elizabeth WarrenOvernight Defense: Appeals court revives House lawsuit against military funding for border wall | Dems push for limits on transferring military gear to police | Lawmakers ask for IG probe into Pentagon's use of COVID-19 funds On The Money: Half of states deplete funds for Trump's 0 unemployment expansion | EU appealing ruling in Apple tax case | House Democrats include more aid for airlines in coronavirus package Warren, Khanna request IG investigation into Pentagon's use of coronavirus funds MORE's (D-Mass.) presidential bid.

"They don't want to do something which makes it more likely for Elizabeth Warren to become president or for us to lose the Senate. So they don't want to go out and criticize the leader of our party because they feel that might have the consequence of hurting our country longer term," Romney told "Axios on HBO."

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"People ... genuinely believe, as I do, that conservative principles are better for our country and for the working people of our country than liberal principles and that if Elizabeth Warren were to become president, for instance, or if we were to lose the Senate, that it would not be good for the American people," Romney added.

Warren, a candidate for the Democratic nomination for president, has surged in the polls in recent months and has overtaken former Vice President Joe Biden Joe BidenFormer Pence aide: White House staffers discussed Trump refusing to leave office Progressive group buys domain name of Trump's No. 1 Supreme Court pick Bloomberg rolls out M ad buy to boost Biden in Florida MORE in some early primary state polling.

Romney, a freshman senator from Utah who was elected last year, has emerged as one of Trump's strongest critics on the GOP side of Congress amid the Democrats' ongoing impeachment inquiry and the president's decision to withdraw troops from northern Syria.

Trump, meanwhile, has regularly attacked Romney via his Twitter feed and earlier this month suggested that the Utah Republican should be "impeached," though there is no mechanism to do so.

"I’m hearing that the Great People of Utah are considering their vote for their Pompous Senator, Mitt Romney, to be a big mistake. I agree! He is a fool who is playing right into the hands of the Do Nothing Democrats! #IMPEACHMITTROMNEY," Trump tweeted.