Sen. Mike Lee (R-Utah) on Tuesday pleaded with his fellow Utahan Mitt Romney, the state’s junior Republican senator, to get off the sidelines and join every other Senate Republican by endorsing him for reelection.

Lee made his case to Romney on Fox News’ “Tucker Carlson Tonight,” where he said that his independent opponent Evan McMullin would vote to keep Sen. Chuck Schumer (D-N.Y.) as majority leader if Republicans fail to win control of the Senate.

“My opponent, Evan McMullin, is a Democrat running in disguise. I understand the commitment made by my colleague. I work with him, like him — but here’s the deal: I don’t think Mitt Romney wants Chuck Schumer to continue to be the Senate majority leader,” Lee said.

Lee urged Romney to “get on board” with every other Senate Republican who has already endorsed him against McMullin.

“Mitt, if you’d like to protect the Republican majority, give us any chance of seizing the Republican majority once again — getting it away from the Democrats who are facilitating this massive spending spree and a massive inflationary binge — please, get on board. Help me win reelection. Help us do that,” he said.

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Last month, Lee posted a list of endorsements from 48 of his Senate Republican colleagues that notably excluded Romney.

Though both Utah lawmakers claim to be conservatives, they differ when it comes to former President Donald Trump. Romney is a longtime Trump critic and was the only GOP senator to vote to convict the Republican president in both of his impeachment trials. Lee, on the other hand, supported Trump’s effort to challenge the results of the 2020 election and criticized the second impeachment effort against Trump as an overreach by Democrats.

While Utah is a red state where typically the two-term Lee would win reelection easily, McMullin has shaken the race up by running as an independent and convincing the Democratic Party not to field a candidate. An ex-CIA agent, McMullin previously ran for president as an independent against Trump and Hillary Clinton in 2016. He is attempting to build a coalition of Democrats and anti-Trump Republicans to unseat Lee, and polls show he is closer to winning than any Democratic candidate who’s faced the incumbent Republican before.

Earlier this year, Romney told reporters that he considers both Lee and McMullin to be friends and said he intended to remain neutral.

“I don’t think endorsements make any difference in a race to speak of. People in the race are my friends. I usually try and avoid situations where they’ve been friends. I may endorse and I may not, but I really haven’t given it any thought at this point,” he said on a video conference call in March.

Lee told host Tucker Carlson that Romney’s neutrality amounted to “tacit assistance” of his opponent.

“Evan McMullin continues to raise millions of dollars from progressive Democratic donors nationwide who are hellbent on getting rid of me,” Lee said.

“I think a lot of Utahans are being duped or fooled, and it doesn’t help to have tacit acquiescence, the tacit assistance of my Republican colleague from Utah.”