JEFFERSON CITY, Mo. -- Sen. Kit Bond, who rose from Missouri's youngest governor to its senior Republican statesmen and a leading national voice on intelligence issues, declared Thursday he will not seek re-election in 2010.

Bond, 69, returned to his political roots in the Missouri Capitol to announce his retirement in front of state lawmakers. The impending political void set off a candidacy scramble.

Among the most prominent likely candidates: Republican Rep. Roy Blunt, who recently stepped down as House minority whip, and Democratic Secretary of State Robin Carnahan, daughter of the late Gov. Mel Carnahan and former senator Jean Carnahan.

Outgoing Missouri Gov. Matt Blunt said his father is "seriously considering" the Senate race. A Carnahan confidant said she also is likely to run.

U.S. Rep. Jo Ann Emerson, R-Cape Girardeau, declined to comment on whether she is interested in the job. "Today is a day to talk about what a great job he has done as senator and how important he has been to the state and what a huge loss to the state his retirement is."

Bond's political career has spanned parts of five decades, beginning with an unsuccessful congressional campaign in 1968. At age 33, he became Missouri's youngest governor, then lost a re-election bid, only to bounce back and win a gubernatorial rematch four years later.

Bond first was elected to the Senate in 1986 -- the only Republican to capture a seat previously held by a Democrat that year. Had he run again and won, Bond would have become Missouri's oldest-ever senator by the time his fifth term ended.

On Thursday, Bond was ushered into the House chamber as a special guest while holding the hand of his wife, Linda. He ascended the dais and delivered a speech urging bipartisanship and recounting his career priorities. After 13 minutes of talking, Bond paused, poured a glass of water, took a long drink and declared: "Now for the tough part."

"Public service has been a blessing and a labor of love for me. Little in life could be more fulfilling, but I have decided that my Senate career will end after this, my fourth term," he said.

Bond added: "In 1973, I became Missouri's youngest governor. I do not aspire to become Missouri's oldest senator."

Asked later if any particular health concern was prompting his decision, Bond instead rattled off a long list of surgeries, aches and pains he's had over the years, even recalling the time he got punched on the Senate floor in 1993.

"Growing old is not for sissies," Bond said, later adding: "I'd like to retire while I'm still at the top of my game."

A native of rural Mexico, Mo., Bond has been the most consistent face of the Missouri Republican Party for several decades.

In the Senate, he became vice chairman of the Intelligence Committee in late 2006 and later played a key role in bringing both parties together to revise the 30-year-old Foreign Intelligence Surveillance Act, a feat he considered one of his greatest accomplishments as a lawmaker.

Bond has seen negative headlines in recent months.

Trevor L. Blackann, a former legislative aide to Bond and Roy Blunt, pleaded guilty in November in federal court to not reporting more than $4,100 in illegal gifts from lobbyists on his 2003 tax forms. Also last year, a Justice Department report found that the senator's office pushed the White House to dismiss then-U.S. Attorney Todd Graves for political reasons. That came after friction between Bond's staff and the staff of Graves' brother, Rep. Sam Graves, R-Mo.

As recently as a few months ago, Bond had told crowds that he planned to seek re-election in 2010. His chief of staff had moved home to Missouri from Washington, a change seen by Republicans as a strong sign Bond was laying the groundwork for another campaign.

Republican consultant John Hancock, who worked for Bond's campaign in 2004, said he attended an organizational meeting in November for Bond's 2010 campaign and had polled Bond with a 58 percent approval rating in December.

"I fully expected Kit Bond to be running for re-election," Hancock said.

Bond told reporters he decided not to run after discussing his future with his family over the Christmas holiday. Bond spokeswoman Shana Marchio said he told her of his decision last week but did not inform his full staff until a Thursday morning conference call.

"I knew he was thinking about it, but I was preparing for him to run," Marchio said. "We were going full-throttle."

Bond's retirement is the second political jolt to the Missouri Republican Party in as many years.

In January 2008, Republican Gov. Matt Blunt announced he would not seek a second term. A contentious two-way Republican primary resulted, and Democrat Jay Nixon ultimately won the governorship in November.

Bond said he announced his retirement nearly two years in advance to give time for potential successors to build their campaigns. He endorsed no one on Thursday but did not rule out that possibility once the field becomes clear.

Asked if he was considering running for the Senate, Matt Blunt on Thursday instead endorsed his father, Roy Blunt. The governor said Roy Blunt is "seriously considering" the Senate race.

"Lots of people are asking him to do it, both in Missouri and across the country, and I think that's a sign that it makes sense," Matt Blunt said.

Outgoing State Treasurer Sarah Steelman, of Rolla, who lost in the 2008 Republican gubernatorial primary, also told the AP she is considering a 2010 Senate run as a result of Bond's departure.

Steelman based her failed gubernatorial bid against Rep. Kenny Hulshof largely on criticism of what she described as wasteful, earmark spending in Washington. Bond has been a staunch champion of earmarks, using a seat on the powerful Senate Appropriations Committee to bring projects to Missouri.

Other possible GOP candidates to replace Bond include Hulshof, of Columbia; former Sen. Jim Talent, who lost a re-election bid in 2006; Rep. Sam Graves, of Tarkio; and Lt. Gov. Peter Kinder, of Cape Girardeau, who declined Thursday to discuss whether he was interested in running.

The Missouri Democratic Party moved quickly to cast Carnahan as its frontrunner.

"Robin would be a strong candidate and a great senator and Democrats across the state hope she'll run," state party executive director, Craig Hosmer, said in a written statement.

Incoming Democratic Attorney General Chris Koster also threw his support behind Carnahan.

A source close to Carnahan, who spoke on the condition of anonymity because the person isn't authorized to speak publicly about her intentions, said Carnahan had been considering a 2010 Senate bid even before Bond's announcement and is likely to run. An announcement could come in the near future, the source said.

Staff writer Rudi Keller contributed to this report.