JEFFERSON CITY, Mo. -- Republican Lt. Gov. Peter Kinder says he is running for governor. And unlike the incumbent, Matt Blunt, Kinder vows he won't change his mind.

Kinder on Thursday became the first Republican to declare that he is definitely in the governor's race since Blunt's surprising announcement that he will not seek a second term.

"I'm in," he said. Asked if there was any scenario in which he would not run, Kinder replied: "No. Crossed the Rubicon."

Blunt's announcement Tuesday ignited a chaotic scramble among Republicans, with at least a half dozen other politicians also testing their support for a potential gubernatorial bid.

Several talked up their credentials Thursday. Among those: U.S. Rep. Jo Ann Emerson, State Treasurer Sarah Steelman, federal prosecutor Catherine Hanaway, House Speaker Rod Jetton and Senate Majority Leader Charlie Shields.

U.S. Rep. Kenny Hulshof remained publicly silent, though others confirmed he is considering the race. A Hulshof candidacy could persuade allies such as Hanaway and Jetton not to run.

State Attorney General Jay Nixon currently is the only Democrat running for governor.

Kinder, of Cape Girardeau, has been the most assertive about his intentions from the outset. Within hours of Blunt's announcement, Kinder issued a statement suggesting that he was likely to run and declaring himself a "change agent."

Kinder said he slept only 90 minutes that night, as he churned over the governor's race in his head, then "plunged through the day" Wednesday, "making dozens of calls" seeking both verbal and financial support for a gubernatorial campaign.

His message to prospective supporters, Kinder said, highlights that he led the Republican takeover of the Senate in 2001, became the chamber's first GOP leader in 53 years, then built the Republican majority to its highest point in Missouri history before he was elected lieutenant governor in 2004.

Others appeared to edge closer to entering the race.

Steelman said she was "thinking very seriously about it" and would announce her intentions "very soon."

Emerson, also of Cape Girardeau, said Thursday that she could draw support from independents and Democrats if she decides to run for governor, a decision she would make by next week.

"I don't know where it's going to lead," Emerson said. "I've been talking to a lot of people, really looking at the situation."

House Speaker Rod Jetton, of Marble Hill, said he has drawn support for a bid from likely donors, fellow House Republicans and local Republican leaders. The only people he still needs to convince are his family members, Jetton said.

Asked if he had the desire to run, Jetton responded: "If my wife is supportive of it, yeah."

But Jetton added he would not run if either former senator Jim Talent or Hulshof, of Columbia, enters the race. Neither of those men has publicly stated their intentions.

Hanaway said she is "still seriously considering" the governor's race but may not make a decision for a couple of weeks.

"I am the only person who has run campaigns and been the candidate," said Hanaway, of suburban St. Louis. "So fortunately, or unfortunately, I have a crystal clear view of what it's going to take to do this in 10 months' time."

Shields, of St. Joseph, said he, too, is "seriously considering running for governor." But Shields added that he also is looking at the lieutenant governor's office, which would be open because of Kinder's decision.

"I'm interested in higher education issues, early childhood issues, job creation, and the governor's office has a unique ability to move that kind of agenda forward," Shields said. "I've always thought that would be an exciting position."

Kinder's decision to run for governor already has had a trickle-down effect.

Former state representative Jack Jackson, who after Blunt's announcement pondered a gubernatorial bid, said Thursday that he instead will run for lieutenant governor. Jackson plans a formal announcement today at the Capitol.

A retired Marine combat pilot, Jackson said the lieutenant governor's duties dealing with seniors and veterans issues were a perfect fit for him.

"I think I would really like that job," said Jackson, of Wildwood, who narrowly lost the Republican primary for auditor in 2006.

Candidacy filing for Missouri's Aug. 5 primary elections runs from Feb. 26 to March 25.