- President Donald Trump has taken a sharp tone with Senate Republicans lately
- Susan Collins was among three GOP senators to oppose an Obamacare repeal
Collins, speaking on MSNBC, also said she was uncertain whom she would back for president during the next election cycle. The Maine senator, who was one of three Republican senators
to vote against a GOP-leadership-backed Obamacare repeal measure last month, noted that she wrote in House Speaker Paul Ryan for president last year.
"I didn't support the President when he was our party's nominee," Collins said. "That was a very difficult position for me to take. I'd never taken it before. Instead, I wrote in the name of Paul Ryan. And that was very hard for me to do, as a lifelong Republican."
Asked if she thought Trump would be the Republican Party nominee in 2020, Collins replied: "It's too difficult to say."
Trump has taken a sharp tone with Senate Republicans lately, blasting Senate Majority Leader Mitch McConnell for not successfully shepherding the Obamacare repeal measure. He has also taken to blasting his critics from the center and the right, including Collins and Sen. Jeff Flake, an Arizona Republican.
Trump is scheduled to host a rally in Phoenix Tuesday night, where both home-state senators -- Flake and John McCain -- have been regular critics of his.
Meanwhile, a number of names have been floated as possible contenders to run against Trump for the Republican nomination in 2020, including Ohio Gov. John Kasich, Flake and others. Kasich denied to CNN on Sunday
that he is planning to challenge Trump, saying he hopes "for him to get it together."