Republican Sen. Wayne Allard announced today that he will not seek re-election in 2008, opening up the Republican side of the field for a race that will be considered one of the top battles in the country.

Former Rep. Scott McInnis (Grand Junction) has already said that he would run for the Senate if Allard retired, which had been expected. McInnis will be a formidable foe for other Republicans because he already has $1 million in his warchest left over from the congressional seat (CD-3) that he left prior to the 2004 election. Republicans are now waiting to see if former Rep. Bob Schaffer, who left his seat in CD-4 prior to the 2002 election, will enter the race for the second straight cycle; Schaffer lost a bitter GOP primary to Pete Coors in 2004 and is a favorite of conservatives.

Former Gov. Bill Owens and Rep. Tom Tancredo have also been mentioned as candidates, and of the two it is much more likely that Tancredo might run than Owens. Ultimately, however, I expect the Republican primary to be a battle between McInnis and Schaffer.

On the Democratic side, Rep. Mark Udall has already said that he will run in 2008.