The top three Democratic contenders to replace retiring Republican Sen. Ben Nighthorse Campbell (search) set aside their differences and cleared the way for Colorado Attorney General Ken Salazar (search) to run.

Rep. Mark Udall (search) and millionaire Rutt Bridges (search) both bowed out Wednesday and promised to support Salazar, considered a friend to Democrats and Republicans throughout the state.

Salazar's decision to run came a week after Campbell abruptly announced he would not seek a third term because of health concerns.

Republicans continued to search for a candidate. GOP Gov. Bill Owens (search) said Tuesday he won't run.

Udall, 53, son of former Rep. Morris "Mo" Udall of Arizona, had announced his candidacy just one day earlier, saying he believed the nation "is on the wrong track." He touted his environmental record and promised to help bring U.S. troops home from Iraq.

On Wednesday, Udall said Salazar would work on those issues. "Maybe this was the shortest Senate campaign in history," he said.

Sen. Jon Corzine (search), chairman of the Democratic Senatorial Campaign Committee, praised Udall and Bridges for helping avert a bruising primary before what could be one of the nation's closest general races.

Corzine said Democrats in North Carolina, South Carolina and Oklahoma have also avoided competitive primaries for open seats in the Senate, where Republicans currently hold a 51-48 majority.

In announcing his bid, Salazar referred to his Hispanic heritage, saying his family's Western roots stretch back four centuries.

"Today I want to help the people of Colorado and our country achieve the same American dream that I have been able to live," said Salazar, 50. "I will do so through my service as a United States senator for the people of Colorado."

Pollster Floyd Ciruli said Salazar has won two statewide races and is seen as more centrist than other Democrats.

"He's the one person you don't want to run a primary against," Ciruli said.

Two other Democrats in the race, educator Mike Miles and lawyer Brad Freedberg, said they will stay in the race. Lawyer Larry Johnson and businesswoman Elizabeth Baker have indicated they may withdraw.

On the GOP side, Reps. Bob Beauprez (search), Tom Tancredo (search) and Scott McInnis (search) have all said they are interested.

Beauprez spokesman Sean Murphy said Democrats were hurt by their wrangling over a candidate and said Beauprez will wait until next week to announce his plans, in time to prepare for precinct caucuses on April 13.

"We realize we don't have a lot of time," Murphy said.