Republican Sen. Mitt Romney told Axios' Mike Allen in an interview with "Axios on HBO" that he believes Republican lawmakers stay quiet on their Trump criticisms for fear of losing the Senate or the presidency to Democrats, especially Sen. Elizabeth Warren.

The big picture: Republicans are often willing to criticize the president privately, but they avoid making public statements for fear of backlash. Romney argues that conservatives are trying to maintain the perception of a united front to voters so as not to risk internal shakeups that could lose them the Senate or Oval Office.

Warren has also been rising in the polls, challenging polling leader Joe Biden and bringing progressive policies to the forefront of the Democratic primaries.

Romney told "Axios on HBO":

"There's no upside in going on out and attacking the leader of your party, 'cause that's just gonna let someone come in and primary you on the right. So people want to hang onto their job."

in going on out and attacking the leader of your party, 'cause that's just gonna let someone come in and primary you on the right. So people want to hang onto their job." "But there's another reason, which is more elevated . And that is 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."

. And that is 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." "And 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."

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