Osborne ended weeks of speculation with the announcement Thursday in his hometown at Hastings College, his alma mater, where he excelled as a three-sport star.

Osborne, a Republican, said he had been contemplating whether to run since Rep. Bill Barrett announced in October that he was retiring at the end of his fifth term.

"I don't think this is an ego trip," Osborne said at a news conference with his family and friends. "It would be a lot easier to go fishing."

Speculation that Osborne might run for office started two weeks ago, after Democratic Sen. Bob Kerrey first hinted that he would not seek re-election. Osborne said Thursday that he never gave serious thought to the Senate.

"The options I had were the 3rd District race or nothing at all," Osborne said.

Osborne, 62, retired after the 1997 season because of a heart condition and to spend more time with his family and humanitarian work.

Osborne said his health is not a problem.

"We did every test known to man on me and found out I had a few miles left in me," he said.

The soft-spoken Osborne holds a doctorate in educational psychology and has long been politically active as an advocate for families, youth and environmental causes. Since his retirement, he has been active in the TeamMates youth-mentoring program he started with his wife, Nancy.

Osborne has never ruled out an entrance into politics since his retirement. He has admitted that he has been restless since leaving coaching.

Several potential Senate candidates had said they were holding off on decisions until Osborne announced his intentions.

Osborne said he decided last week to enter the race after another GOP candidate, John Hanson of Bertrand, Neb., asked the retired coach to run.

"This is the right man for the right time," said Hanson, a farm credit services manager. "I will do everything I can to support Tom and make sure his message gets across."

Osborne faces several relatively unknown GOP candidates in the May 9 primary.