The article overstates its case when it describes Rehberg as "wildly popular", but you're on the money when you say he's the best candidate available. He would definitely be the favorite against John Morrison (the likely Dem. nominee).
And how's this for a senario: ex-Gov. Marc Racicot runs for the House to succeed Rehberg, then challenges Max Baucus in 2010?
Racicot could have challenged Baucus in 2002 but declined.
Racicot wouldn't run for the House for all the tea in China. If he was "too good" to run for the Senate in 2002 (when he would have trounced Baucus), why would he run for a 2-year term to be one of 435?
Hopefully Racicot will reconsider and run against Baucus in 2008 (which is when the seat comes up), but the GOP would need another candidate to run for the House.
As for exactly how popular Rehberg is, I think you're right that "wildly popular" is a bit hyperbolic, but Rehberg has gotten over 60% in his House reelection races. Unless a higher-profile Democrat runs, Rehberg will win the Senate race.
Yeah, Racicot is not going to run for the House seat, period. In fact, if Rehberg vacates the seat to run for the Senate, we may have considerable difficulty holding the House seat because we have no one warming up in the bullpen. I heard some vague rumors about ex-Congressman Rick Hill making a comeback (he was forced into retirement when he was quickly facing the prospect of losing his eyesight), since apparently his health problems were corrected (I could be wrong, but that's what I heard).
The only other GOP statewide officeholder is the Secretary of State, Brad Johnson, and I don't know if he'd be anxious to jump into an open-seat House race.
Former Lt Gov Karl Ohs (the current state party chair) might also be a decent candidate.
There's no way Raicoit would run for House. If he wants back in, it's him that should succeed Burns and Rehberg should stay where he is and run against Baucus in 2008.
But either way is fine for me. I think one or the other should probably signal primary challenge at this point. It would make sure Burns will retire, because either would probably win if he ran.