Attorney General Ken Salazar (search) has quickly moved from the Democrats' best chance of reclaiming the governor's office in 2006 to one of his party's brightest hopes of retaking the U.S. Senate majority.

Salazar, 49, declared his candidacy last week for the Senate seat being vacated by two-term Republican Ben Nighthorse Campbell (search). He was joined at the news conference by Rep. Mark Udall (search) and think tank founder Rutt Bridges (search), two leading Democratic candidates who simultaneously dropped out of the race when Salazar entered.

Political observers were surprised not only by the show of unity but by Salazar's decision to run for Senate rather than the governor's office, which was long seen as his goal.

"Everybody assumed that Salazar was going to run for governor and that his ambition was to stay in Colorado," said GOP political consultant Katy Atkinson. "I don't think people expected him to look to Washington."

He still must face two lesser-known candidates in the Aug. 10 primary, El Paso County educator Mike Miles and lawyer Larry Johnson. In the GOP primary, former Rep. Bob Schaffer will face retired Air Force Academy law professor Dan O'Bryant.

Although Salazar has opponents in the primary, he is the Democrats' strongest candidate and will be a tough opponent in the general election, said University of Virginia political scientist Larry Sabato.

Salazar's roots in Colorado are deep. His family ranches in southern Colorado and he has worked off and on in state government since 1986, first as former Gov. Roy Romer's chief legal counsel and then as head of the state Department of Natural Resources.

In private law practice and government, Salazar has become a leader on the state's complex water problems. He campaigned against a $2 billion water projects proposal that was assailed as a blank check. It was soundly defeated by voters last November.

He wrote the constitutional amendment that created Great Outdoors Colorado, which uses state lottery funds for parks, trails, open space and recreation, and was the program's first chairman.

Salazar said the same issues that interested him in the governor's office are behind his run for the Senate.

"I care a lot about our natural resources and about the beauty of Colorado," he said. "Our quality of life is very much dependent on our being able to maintain our natural heritage."

The second-term attorney general said he also is concerned about enabling law enforcement to deal with the challenges of homeland security.

Salazar narrowly defeated his GOP opponent in 1998 and won re-election in 2002 with 58 percent of the vote. His two successful statewide campaigns and his image as a moderate Democrat are among his pluses as a candidate, political experts say.

"Every campaign he's run, he's had Republicans and unaffiliateds as part of his campaign. He has the respect and affection of lots of different groups," said former Democratic Gov. Dick Lamm.

Colorado's Senate seat was seen as safe for the GOP when heavily favored Campbell was running, but is now a focal point for the national parties as they battle for control of the Senate. Republicans hold a 51-48 majority with one Democrat-leaning independent.