DAYTON, Ohio — On his 72nd birthday, Sen. John McCain rattled the dynamic of the presidential race by choosing Alaska Gov. Sarah Palin, a little-known, tough-talking social conservative with corruption-fighting credentials, to be his running mate.

Saying he has found "the right partner to help me stand up to those who value their privileges over their responsibilities," McCain introduced the 44-year-old, first female governor of Alaska, to an exuberant stadium filled with more than 12,000 voters yesterday — the largest crowd of his campaign.

She "knows what it's like to worry about mortgage payments and healthcare and the cost of gasoline and groceries," said McCain, who first met Palin in February. "And I am especially proud to say in the week we celebrate the anniversary of women's suffrage ... a devoted wife and a mother of five."

The surprise choice of Palin guarantees that either a black person or a woman will ascend to the White House for the first time in history next year.

McCain, no doubt looking to recapture his image as a maverick reformer, settled on Palin as his running mate six months after first meeting the governor and following only one phone call between them last Sunday and a single face-to-face meeting Thursday, according to a timeline provided by his campaign.

In picking Palin, McCain reached out to women voters, union members and people worried about the economy. He also reassured social conservatives and evangelical voters with Palin's strong anti-abortion, anti-gay marriage stance.

Sen. Barack Obama's spokesman, Bill Burton, derided the pick, as did Democratic lawmakers and liberal interest groups, many of them calling Palin's selection "a Hail Mary pass" and a sign of "political panic."

"Today, John McCain put the former mayor of a town of 9,000 with zero foreign policy experience a heartbeat away from the presidency," Burton said. "Governor Palin shares John McCain's commitment to overturning Roe v. Wade, the agenda of Big Oil and continuing George Bush's failed economic policies — that's not the change we need, it's just more of the same."

Jill Hazelbaker, a spokeswoman for McCain, said, "She has a record of accomplishment that Senator Obama simply cannot match. Governor Palin has spent her time in office shaking up government in Alaska and actually achieving results — whether it's taking on corruption, passing ethics reform or stopping wasteful spending and the 'bridge to nowhere.' Senator Obama has spent his time in office running for president."

Palin, accompanied by her husband, Todd, a member of the steelworkers' union and a world champion snow machine racer, and four of her five children, said she was honored by McCain's confidence in her.

"The next 67 days, I'm going to take our campaign to every part of our country and our message of reform to every voter of every background in every political party or no party at all," said Palin, who described herself as an "average hockey mom" before entering politics.

ATTEMPT TO WIN VOTERS

In deciding on a running mate, McCain passed over Minnesota Gov. Tim Pawlenty, former Massachusetts Gov. Mitt Romney and Connecticut Sen. Joe Lieberman, among others.

In the end, McCain chose a running mate who got her political start in the PTA and would help strengthen his ties to the far right of his party, appeal to women who are not enamored with Obama, and reach out to blue-collar workers in the industrial states of Ohio, Michigan and Pennsylvania that he has to win.

Palin, McCain told the crowd, "was a union member and is married to a union member and understands the problems, the hopes, the values of working people."

Besides being a social conservative, Palin is a member of the National Rifle Association and is wildly popular in Alaska. Her oldest son enlisted in the Army and deploys to Iraq in September. And her youngest son — just born in April — has Down syndrome.

Palin paid tribute to Sen. Hillary Clinton, who won 18 million votes in the Democratic primary, but not her party's nomination. And she acknowledged Geraldine Ferraro, the first woman nominated for vice president.

"I can't begin this great effort without honoring the achievement of Geraldine Ferraro in 1984 and of course, Hillary Clinton, who showed determination in her presidential campaign," Palin said. "It was rightly noted in Denver this week that Hillary left 18 million cracks in the highest, hardest glass ceiling in America. But it turns out the women of America aren't finished yet, and we can shatter that glass ceiling once and for all."

Clinton congratulated Palin and McCain for her "historic nomination," but noted that the ticket's policies "would take America in the wrong direction."

For her part, Ferraro, who was Walter Mondale's running mate in 1984, told Fox News that "there are a lot of women who are disaffected by how Hillary was treated by the media, by the Obama campaign, by how she was treated by the Democratic National Committee, Howard Dean not speaking up when sexism raised its ugly head in the media."

ELEVATING REFORMERS

President Bush complimented McCain for "an exciting decision."

"Governor Palin is a proven reformer who is a wise steward of taxpayer dollars and champion for accountability in government," a presidential statement said. "By selecting a working mother with a track record of getting things done, Senator McCain has once again demonstrated his commitment to reforming Washington."

Asked why McCain chose her, his campaign manager Rick Davis said, "Part of it is personal fit."

"He sees Sarah, Governor Palin, as the future of the party," he added. "These are people he'd like to elevate in that regard. Reformers."

Palin's husband is part Yup'ik Eskimo, and is a blue-collar North Slope oil worker who competes in the Iron Dog, a 1,900-mile snowmobile race. The family lives in Wasilla.

The Washington Post and Associated Press contributed to this report.