Never say never. WY Democrats came VERY close to knocking off Rep. Barbara Cubin in 2006 (1,000 vote margin). The advantage Democrats have is that they can conceivably win ANY House seat in the nation under the right circumstances (they have done so in Utah, as an example). Republicans cannot, as there are perhaps 100-150 House seats that have a racial and/or ideological barrier.
Yeah well Cubin always did piss people off, and walking across the stage during a televised debate and saying to your opponent, "If you weren't in that wheelchair I'd slap your face" does tend to alientate the electorate. I doubt that Enzi would do that and I would hope that Cheney wouldn't as well. But you never know.
The advantage Democrats have is that they can conceivably win ANY House seat in the nation under the right circumstances...
The Senate is a little different, and in order to do that they need a candidate, and I don't see who they have in their bullpen who could knock of Enzi. And if Cheney did win then I still don't see that fracturing the party enough to hand it to the opposition. Not with Obama heading the show.