Sen. Ben Nighthorse Campbell’s (R-Colo.) retirement announcement on Tuesday has set off a mad scramble among would-be candidates as they position themselves for the open-seat contest.

“Everyone’s in a state of shock politically out here in Colorado — Democrats and Republicans,” said Sean Tonner, Campbell’s campaign manager.

For now, most of the attention is focused on the Republican side, where sitting Gov. Bill Owens is seen as the strongest potential candidate.

But the Democratic side could also get interesting, with Rep. Mark Udall reconsidering a potential bid. Wealthy philanthropist Rutt Bridges joined the race this week.

Udall would not comment on his future intentions Wednesday. Since Campbell cited health reasons as a major reason for his exit, Udall said he is “first and foremost concerned about Ben’s health” for now.

Owens, who was first elected to the governorship in 1998, was easily re-elected in 2002 and is already being mentioned as a potential contender for the 2008 Republican presidential nomination.

One Republican familiar with the state’s politics said that Owens is “strongly considering” a bid, but added that the governor must carefully weigh his potential interest in the nation’s top office before leaping.

“I could build a case that staying as governor helps that more than running and winning a U.S. Senate seat,” said the GOP strategist.

Owens, who used the same political team for his 2002 re-election that Campbell was using this year, issued a statement praising the Senator’s service but saying nothing about his own political future.

“He only found out this morning,” Owens’ spokeswoman, Kristin Hubble, said Wednesday. “His first thought is with the Senator’s health. He hasn’t thought through the ramifications of this at all.”

If the governor does not run, Rep. Tom Tancredo (R) may jump in, with a spokesman noting that he is “very interested” in the race.

GOP Reps. Scott McInnis and Bob Beauprez said Wednesday that they would give Owens the right of first refusal in the race but would think about a bid if he decided against running.

Campbell’s retirement comes after months of speculation about his political future that had grown to a fever pitch in recent weeks after the resignation of his chief of staff and multiple health problems.

In a statement released by his office, Campbell said that “after spending another night in the hospital I realize that my deteriorating health may hamper my ability to serve.”

Campbell, the lone American Indian in the Senate, was diagnosed with prostate cancer last year and visited the hospital twice in the past week with chest pains.

He had long been rumored as a retirement possibility due to his sluggish fundraising numbers. Those whispers grew louder late last month following the resignation of Campbell’s longtime chief of staff, Ginnie Kontnik, amid allegations that she demanded a kickback from an underling with the Senator’s tacit approval.

His retirement comes nine years to the day that he switched from the Democratic to the Republican Party.

The newly open seat comes just days after Democrats seemed to have settled on Bridges as their candidate culminating more than a year of searching in vain for a serious contender.

In his statement on Campbell’s retirement, Democratic Senatorial Campaign Committee Chairman Jon Corzine (N.J.) praised Bridges, adding: “Today’s developments only increase our chances of winning in Colorado.”

Bridges has pledged to spend between $5 million and $10 million of his own money on the race and may benefit from the silent support of some establishment Democrats attracted to his ability to finance the race.

“Regardless of what Udall decides to do or anybody else, Rutt Bridges is in this for the duration,” said Susan Bachar, his campaign spokeswoman.

Udall’s renewed interest comes after flirting with a bid for much of 2003 only to announce in December that he would forgo a challenge to the incumbent and instead seek a fourth term to his Boulder-based 2nd district.

As Bridges prepared to enter the race late last week amid rampant speculation about Campbell’s future, Udall placed calls to high-level Democrats in the state asking them to hold off on an endorsement as he was reconsidering the race.

Udall is seen by most Democrats in Washington as their strongest possible Senate candidate. First elected in a highly contested 1998 open-seat contest, Udall has held the seat easily since.

He is the son of late Arizona Rep. Mo Udall (D), a presidential candidate in 1976, and the nephew of former Interior Secretary Stewart Udall. His cousin, Tom, currently holds New Mexico’s 3rd district.

Rep. Diana DeGette (D-Colo.) issued a statement Wednesday saying she is also considering the race.

On the Republican side, the makeup of the field will largely depend on Owens’ decision.

Aside from his considerations about the potential impact of a Senate race on his presidential aspirations, Owens must also deal with the issue of his separation from his wife, which became public last fall.

Republicans wondered privately Wednesday whether Owens wants to further air his personal matters in a Senate race.

Colorado Democratic Party Chairman Chris Gates, meanwhile, wasted no time in taking a preemptive shot at Owens: “We would relish the chance to have a statewide debate with Governor Owens about the state of Colorado’s economy and the state of Colorado’s budget and fiscal policy.”

Tancredo, who has held the 6th district since 1998, is seen as likely to enter the race regardless of Owens’ decision.

“Colorado and the country are going to miss Uncle Ben,” said Tancredo spokesman Carlos Espinosa about Campbell’s decision.

But he added, Tancredo is “definitely keeping his options open” and sees the Senate as a “much larger megaphone” for his issues.

A knowledgeable state Republican said that while Owens would almost assuredly triumph in a primary against Tancredo, it would be a “pretty strong diversion” as the GOP prepares for November.

Tancredo is one of the most conservative members of the House Republican Conference and has been an outspoken critic of President Bush’s immigration policies.

McInnis and Beauprez are both seen as serious contenders if Owens decides against the race. Beauprez said he was completely blindsided by Campbell’s decision and that he was not yet ready to answer a question about his own future.

“I would have to wait for the dust to settle before I would respond,” Beauprez said.

Beauprez won the new 7th district — located in the Denver suburbs — by just 121 votes last cycle.

Although he has spent barely more than a year in the seat, Republican observers believe his representation of Jefferson and Arapahoe counties — two Republican strongholds in the state — could position him well in a GOP primary.

McInnis, who is retiring from his 3rd district seat at the end of the year, said that he had “not made any decision” about the Senate race, though he pointed out that he would be on strong financial footing if he decided to run.

McInnis showed $1.4 million in the bank at the end of 2003. Beauprez had $793,000 on hand and Tancredo $501,000 at that time.

Lt. Gov. Jane Norton and 4th district Rep. Marilyn Musgrave are also mentioned as possible candidates on the GOP side, but neither is expected to make the race.

Ben Pershing, Erin P. Billings, Paul Kane and Josh Kurtz contributed to this report.