By Andy Matthews

Republicans' plans to increase their Senate majority this year hit a snag when Colorado's Ben "Nighthorse" Campbell announced he will not seek re-election in November, thus putting what had been a safe GOP seat in play.

And the party's woes were exacerbated when the state's popular governor, Republican Bill Owens, decided not to run for the nomination to replace Campbell despite speculation he would. An Owens candidacy almost certainly would have kept this seat in the Republican column, but now, it's anybody's guess which way this one will turn.

The overall Senate outlook remains positive for Republicans, even with Colorado up in the air. With five Southern Democrats retiring from the Senate this year, plus John Thune's challenge to Tom Daschle in South Dakota, the GOP's prospects for building on its 51-seat majority remain strong. Still, with things as tight as they are in that chamber, every seat counts, and the decisions of Campbell and Owens have given the party some cause for concern.

So what of this Colorado race? Can the GOP win without Campbell or Owens as the nominee? Most signs point to a general-election contest between Colorado Attorney General Ken Salazar (D) and former congressman Bob Schaffer (R) in what promises to be one of the more interesting contests of the year. Salazar begins the campaign with a significant advantage in name recognition, but it would be a mistake to discount the Republican in this pro-GOP state. My guess is this race will be a tight one, with Schaffer chasing Salazar in the polls initially but narrowing the gap as the campaign season progresses.

But enough about that. The implications of the recent developments in Colorado extend beyond this year's Senate race. In fact, it may be that the biggest story here has to do neither with Campbell's retirement nor with the two frontrunners to replace him. The key here is Owens.

As one of the nation's most popular (and best) governors, Owens is widely touted as a potential presidential candidate for 2008, and his decision not to jump in the Senate race serves as strong evidence that he will in fact make a run at the Oval Office.

While a successful Senate bid no doubt would have provided him some positive publicity (and endeared him to the party for helping save Campbell's seat), Owens seems to have calculated that his chances of becoming president would be greater if he were to run as a sitting governor rather than as a senator.

If that's his thinking, he has indeed made the right call. History has shown time and again that governorships are a far better launching pad to the presidency than the Senate is. There are several reasons for this, but chief among them is the fact that senators tend to rack up a long list of votes that can be used against them during presidential campaigns (John Kerry is now getting and will continue to get a painful lesson in this).

Granted, if Owens were to replace Campbell and then still decide to run for president in '08, he would have been in the Senate for just a short time and wouldn't provide his opponents with nearly as much ammo as a career legislator like Kerry will. But why take the chance? Better to stay put for now, and run for president as a popular governor (as George W. Bush did in 2000, to cite just one example).

In the short term, Owens' decision not to enter the Senate race is bad news for Republicans, who also face tough battles to hold onto seats in Illinois, Alaska and Oklahoma this year.

But even if Campbell's seat does move into the Democratic column, the fact that Bill Owens will be better positioned for a presidential run will be a major plus for the party -- and the country -- down the road.

Andy Matthews is the editor of rightturnonly.com.