DENVER -- Sen. Ben Nighthorse Campbell officially launched his re-election bid Thursday, saying his prostate cancer is under control after radiation treatment.

The Colorado Republican was diagnosed with cancer a year ago and advised by doctors to try to control it with diet. When that failed, he underwent a series of radiation treatments this fall.

"I'm done with the treatment now. I feel just fine. I tell people, to quote Mark Twain, the reports of my demise have been greatly exaggerated," he said.

Campbell, 70, was to be joined by Vice President Dick Cheney at a 2004 campaign kickoff and fund-raiser later Thursday.

The event, expected to raise $500,000, will be held downtown Denver at the Hyatt at 6 p.m.

Campbell said officials at the White House asked him to run again, as part of an effort to break a 50-50 deadlock in the Senate.

If he wins, Campbell said it could be his last term.

"I think you should stay as long as you feel you are making progress, getting things done, and you feel good about the job," he said. "But when you reach a point where you stagnate, you are not moving anything, you're disliking it, you ought to leave. I haven't reached that point."

Campbell's only opposition is from two Democrats, Colorado Springs educator Mike Miles and Denver lawyer Brad Freedberg.

Rep. Mark Udall, D-Colo., and former Democratic Sen. Gary Hart have discussed challenging Campbell, but neither has declared his candidacy.

Hart declined comment Thursday. Udall's spokesman did not return a telephone message seeking comment.

Campbell's cancer was detected through a screening last year. "It comes with the age now, it's part of a high-fat diet," he said.

"Women's breast cancer is out in the open. People talk about it regularly, it's a normal thing almost. Men tend to be less willing to talk about it so much, or maybe it's not considered a macho thing to admit you got sick," he said.

Concerns about Campbell's health should not affect his campaign, pollster Floyd Ciruli said. A recent poll gave Campbell a 68 percent support rating.

"Obviously, there is the health question, which he says is manageable. He's also full of surprises, and he follows his own destiny," Ciruli said.

Campbell raised $350,588 from July through September, bringing his total fund-raising to more than $1.2 million, with $965,000 in the bank. He predicted he would raise $2 million by the end of this year.

Miles criticized Campbell's fund-raising and said he will focus on issues, like education. "If the political process is all about money, then I guess the odds are against me. I'm willing to bet that substance counts," Miles said.

Freedberg said Campbell is vulnerable because he's a Republican.

"He is a member of a party that controls all sectors of our government. We can see that a lack of real debate results in problems like we have in Iraq and a lack of vision," Freedberg said.

Campbell was elected to the House of Representatives as a Democrat in 1986, won his Senate seat in 1992 and switched parties in 1995. He is the only American Indian in the Senate.