ABC News' Rick Klein reports: Sen. Jim DeMint's decision to buck the GOP establishment in a series of Republican primaries has prompted talk that DeMint, R-S.C., may be mulling a challenge to Senate Minority Leader Mitch McConnell’s leadership – a notion that DeMint himself denies. On ABC/Washington Post’s “Top Line” today, one DeMint-backed candidate, Colorado Senate candidate Ken Buck, wouldn’t say directly whether he’d back DeMint in such a bid. Asked whether he’d support DeMint to be Senate Republican leader, Buck said: “I think Jim DeMint has a great voice, and I think he has a voice that's gonna be more and more respected in the United States Senate, and I certainly think that he has a leadership role in the Republican Party in the Senate, absolutely.” Asked whether it’s time for new GOP leadership in the Senate, Buck said: “I'm not gonna go there. I don't know enough. I'm focused on Colorado. I'm focused on trying to win a primary. I haven't dealt with the leadership in DC, and right now, I'm concerned about what's gonna happen on Aug. 10 here in Colorado.” Republicans in Washington, Buck said, “don’t do a very good job” on exercising fiscal discipline once they get to office. “The Republicans talk about it when they're running for office. They unfortunately don't do a very good job of it when they're in DC, and I think that’s what the new generation of Republicans is gonna do when we get there,” Buck said. Buck also had strong words for Democrats, saying that the “progressive liberal movement” represents the “largest threat” to the country, more of a threat even than that posed by al Qaeda or Iran.