MADISON, Wis. -- Lt. Gov. Barbara Lawton told supporters on Monday that she has decided against running for governor of Wisconsin.

READ: Democrats Search For New Gubernatorial Candidate

Lawton sent an e-mail message to her supporters and posted her announcement on her campaign Web site on Monday. The message didn't go into further detail and her campaign spokesman didn't immediately return a message seeking comment.

"My deep commitment to our state is second only to my commitment to my family," Lawton said in a statement posted on her site. "For very personal reasons, I will not pursue the Democratic nomination for governor in 2010."

Calls to the Lawton's office at the state Capitol went unanswered on Monday as it was apparently shut down. Reporters who showed up found the state office doors locked and the lights off, WISC-TV reported.

One supporter, state Sen. Jim Sullivan, said that he talked to Lawton on Monday morning and that she's stepping out of the race for family reasons. Lawton, 58, is married and has two children, and four grandchildren.

"I understand that this is a matter that's of a personal and family nature," Sullivan said, "that kept her from being able to mount a statewide campaign for governor right now, and Ii think we have to respect that."

State Democratic Party Chair Mike Tate also said on Monday that a Lawton aide told him that the Lawton and her husband are not ill.

Some supporters said on Monday that Lawton had been building up for a run for governor her whole career. She was leader in the state progressive movement and became the first female lieutenant governor by running with Gov. Jim Doyle in 2002.

She was considered the frontrunner for the Democratic nomination after Doyle announced that he wouldn't run for another term during the summer. Shortly after Doyle's announcement in August, aides said that Lawton was planning to run for governor in 2010. Lawton had previously said she'd consider running if Doyle didn't seek a third term.

Some of Lawton's friends expressed shock, surprise and concern in the wake of her announcement.

Matt Rothschild, editor of the Progressive magazine, said he had "no inkling" of Lawton's withdrawal until Monday when he heard about her e-mail to supporters announcing it. He said that Lawton was "rarin' to go," had a lot of support from liberals around the state and was very committed to the race for governor. He said he thinks she never would have given that up solely for political reasons, like campaign donations, bad polling numbers or possible Democratic challenger Milwaukee Mayor Tom Barrett.

"I believe firmly that it is something very personal and not something political. Barbara Lawton (is) not someone to step back from a fight. She's not someone who's afraid to go into a contest when maybe she doesn't have more money than the other person or maybe her polls numbers aren't quite as high," he said.

Rothschild said that Lawton had the enthusiastic support of the progressives across the state, who admired her work on women's issues, the environment, health care and the arts.

Assembly Speaker Mike Sheridan, D-Janesville, said that he too was surprised by Lawton's announcement.

He said "it's funny" that no one seems to want the job. As for his own ambitions, Sheridan shied away from saying whether he'd enter the race.

"Certainly, my thoughts are that I never completely pulled my name out. I think there's still a lot of good candidates still in this state under the Democratic Party. So this a wait-and-see, but I want to make sure we have good leadership in the state," he said.

Sheridan said that he thought Barrett would be a strong candidate.

"I just have a tremendous amount of respect for Tom Barrett. I would love to see him as a candidate for governor. I think he's a great leader and could really do a fine job in this state," Sheridan said.

Two prominent Republicans, Milwaukee County Executive Scott Walker and Former U.S. Rep. Mark Neumann, are already in the race.

Since Doyle's announcement, several high-profile politicians have been the subject of speculation about whether they'd run. U.S. Reps. Ron Kind and Paul Ryan, state Sen. Jon Erpenbach were among the candidates rumored to have considered a run but who said that they wouldn't seek higher office.

Barrett has been considering running but hasn't yet announced.

Rothschild said perhaps Dane County Executive Kathleen Falk or U.S. Rep. Tammy Baldwin will consider replacing her, saying it's time Wisconsin had a female governor.

Late on Monday, Falk put out a short statement on Lawton's stepping down from the race, expressing her surprise.

Stay tuned to WISC-TV and Channel 3000 for continuing coverage.