ABC News' Rick Klein reports: Despite tough questioning of Elena Kagan this week, Sen. Orrin Hatch, a senior Republican on the Senate Judiciary Committee, today ruled out a GOP filibuster of Kagan's Supreme Court nomination, saying such a move would be "unheard of" and a "dirty thing to do." On ABC/Washington Post’s “Top Line” today, Hatch, R-Utah, said that while he’s still undecided on whether to support Kagan, she’s almost certain to be confirmed. “The only ones who have ever filibustered a Supreme Court nominee are the Democrats,” Hatch told us. “Republicans aren't gonna filibuster her. I don't think — most Republicans don't believe in it. And I have to say that our president was one of those who did filibuster a Republican nominee. So there's — I don't think you have to worry about Republicans doing that. I think that would be an unheard of, dirty thing to do at this point.” Hatch said he still may vote “no” on Kagan — as he did on Sonia Sotomayor’s nomination – even though he voted to confirm Kagan as solicitor general. “I'm still mulling it over in my mind. I have to say, there are things that really bother me. And there are a lot of things I think are very good about her, as well. She's a very intelligent woman, very personable. Not afraid to express her viewpoint, except she didn't express any of her own viewpoints — she expressed a lot for the administration,” Hatch said. “Keep in mind: The solicitor general's nomination is for a job that only lasts a certain amount of time. This is a lifetime appointment to the most important court in the world, and she'll be one of nine people. And so, you know, it takes a little extra effort, and because I voted for her for solicitor general doesn't mean that I will vote for her for Supreme Court.” Other Republicans on the Judiciary Committee – including Sen. Jeff Sessions, R-Ala., and Sen. Tom Coburn, R-Okla. – have refused to rule out a filibuster of Kagan. But with only 41 Republican senators, a filibuster would have to draw all GOP members to be successful. Sixty senators can vote together to end debate on Senate action, so just one Republican voting with Democrats would be enough to essentially guarantee Kagan’s confirmation. Hatch also had strong feelings about President Obama’s handling of the immigration issue: “You know doggone well there's no way they can put an immigration bill through in the remaining days that we have in this Congress,” he said. And he made clear that he has a favorite in the emerging 2012 presidential race: “It's pretty tough for anybody to be as good as Mitt Romney,” Hatch said. For our “Post Politics” segment, we checked in with Dan Balz of The Washington Post on the president’s immigration push, the Kagan nomination, plus Democratic angst over the war in Afghanistan.