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Republican Gov. Matt Blunt, who had stockpiled millions of dollars for an expected re-election campaign, threw Missouri politics into disarray Tuesday by abruptly announcing his exit from the race.

In the stunning announcement, Blunt said he had decided not to seek a second term because he had accomplished virtually everything he set out to do when he ran for governor four years ago.

But Blunt has trailed in the polls to Democratic Attorney General Jay Nixon, who has been campaigning against Blunt for several years already.

From his first months in office, Blunt has been under fire for slashing the Medicaid benefits of hundreds of thousands of Missourians. More recently, he was sued by a former staff attorney alleging the governor's office illegally destroyed e-mails, then tried to cover it up, to avoid complying with Missouri's open-records law.

No other Republicans had entered the governor's race, assuming the well-financed Blunt made for too stiff of a challenge. But several Republicans quickly began pondering the possibilities. Republican Lt. Gov. Peter Kinder, for one, indicated he likely will run for governor.

Just last week, Blunt delivered his annual State of the State address highlighting his past accomplishments and future spending proposals while giving no indication it would be his last such speech.

In a video statement released Tuesday afternoon, Blunt repeated assertions that he had balanced an out-of-whack state budget, boosted education spending and transformed the state's Medicaid health care system for the poor.

"After a great deal of thought and prayer, and with the knowledge that we have achieved virtually everything I set out to accomplish, and more, I will not seek a second term in the upcoming election," Blunt said. "Because I feel we have changed what I wanted to change in the first term, there is not the same sense of mission for a second."

Blunt also cited a desire to spend more time with his wife, Melanie, and their son Branch, who is almost 3 years old. The Blunts have split their time between the Governor's Mansion in Jefferson City and their personal home in Springfield.

"I have spent more time away from them than I would like," Blunt said. "We are ready for the next chapter in our lives."

Blunt gave no indication of what he intends to do upon leaving office in January 2009. He has been a staunch supporter of Republican Mitt Romney from the very beginning of Romney's presidential bid, helping him to raise money and campaigning for him in and out of Missouri.

Romney praised Blunt as "a conservative leader and dedicated public servant" whose "efforts to improve the lives of others will not end when his term comes to a close."

Republican legislative leaders said Blunt revealed his intentions to them in a conference call shortly before the public announcement. Shock was the universal reaction.

"I'm still dealing with the surprise. I'm sort of dumbfounded," said Senate President Pro Tem Michael Gibbons, adding he would not give up his Republican attorney general's bid to instead run for governor.

But others quickly shifted their thinking.

"I was speechless," said Republican House Speaker Rod Jetton, who also had planned to exit office this year because of term limits. But in light of Blunt's announcement, Jetton said he would now consider running for governor.

"It changes everything," Jetton said.

Kinder issued a statement Tuesday night casting himself as "a change agent" who has worked to improve Missouri's economy, education and health care systems.

"I will formally announce my plans for governor in the coming weeks," Kinder said.

U.S. Attorney Catherine Hanaway, a former Missouri House speaker, said she also is considering the governor's race.

"Whoever is going to do this is going to have to make a decision very quickly," Hanaway said.

Former Republican Rep. Jack Jackson confirmed he also is considering the race anew. Jackson, who ran unsuccessfully for auditor in 2006, conducted polling last year for a potential governor's race but opted against it after an October meeting with Blunt at the Governor's Mansion.

A spokesman for U.S. Rep. Jo Ann Emerson said she, too, was thinking about whether to make a statewide race.

Kinder and Republican U.S. Rep. Kenny Hulshof both considered running for governor in 2004, but deferred to Blunt.

"Congressman Hulshof was very surprised to hear today's news," said Hulshof spokesman Scott Baker. "There's really no additional comment at this time."

Nixon's Democratic campaign had focused heavily on Blunt's shortcomings. Now lacking an incumbent target, Nixon said in a statement, "I will continue to focus on changing the direction of our state so that more Missourians have access to health care, more Missourians can find good-paying jobs and more Missouri children can get the quality education they deserve."

Political scientist David Webber said Blunt's departure would create "a distraction for the Republicans" until the state's August primary elections, especially if no front-runner quickly emerges. That should give Nixon a boost, but may not automatically propel him into office.

"I don't think there's a big vacuum," Webber said. "I think that the Republicans do have a strong party organization and they have experienced candidates, so it shouldn't be hard for them."

Earlier this month, Blunt was sued by a former staff attorney, who claims he was fired and defamed in retaliation for pointing out that Blunt's office was destroying e-mails in violation of Missouri's open-records law. Blunt has defended the September firing of Scott Eckersley, but has declined to comment on the allegations that his office intentionally purged e-mails as a way to avoid providing information under a Sunshine Law request.

Blunt, 37, is the son of U.S. Rep. Roy Blunt. He was the second-youngest Missouri governor when he took office in January 2005, leading Missouri's first Republican-controlled Legislature and Governor's Mansion in about 80 years. He had served the four previous years as secretary of state and before that spent just one term as a state representative from southwest Missouri, from 1999-2001.

The Republican Legislature passed almost every priority Blunt has backed.

Among them: restrictions on liability lawsuits and workplace injury claims; a new school funding method; economic development incentives; tougher penalties on child sex offenders; more stringent laws targeting methamphetamine makers; an ethanol mandate for gasoline; abortion restrictions; more protections against the use of eminent domain; expanded college scholarships; and a $350 million plan to take money from Missouri's student loan authority to finance college buildings.

Yet Blunt is perhaps best remembered for one of his first acts in office — eliminating or reducing Medicaid benefits to hundreds of thousands of low-income Missourians as a way to balance the budget. Nixon has made the 2005 cuts the central point of his campaign against Blunt.

A poll conducted last November for the St. Louis Post-Dispatch and TV station KMOV showed Nixon ahead of Blunt, 51 percent to 42 percent, with a margin of error of plus or minus 3.5 percentage points. It also revealed that 57 percent of the 800 likely voters polled by Research 2000 opposed Blunt's handling of health care. And 61 percent said Blunt's handling of health care would be an important, or very important, factor in deciding their vote for governor.

Blunt had built a big fundraising advantage over Nixon, reporting more than $6 million on hand compared with Nixon's $2.7 million in October. But Blunt's advantage shrunk as a result of a Missouri Supreme Court decision reinstating campaign contribution limits and leading to the refund of large checks.

Last week, Blunt reported $4 million on hand and Nixon $1.7 million, but Blunt still needed to refund more than $2.3 million while Nixon had completed his refunds.