DAYTON, Ohio — Republican Sen. John McCain on Friday picked little-known Alaska Gov. Sarah Palin as his running mate, reassuring anxious social and fiscal conservatives but muting his own attacks on Democratic rival Sen. Barack Obama as too inexperienced to become commander in chief. The stunning choice sets up a truly historic presidential race — on Nov. 4, Americans will either elect the nation's first black president or its first female vice president in the 44-year-old Mrs. Palin.
Mrs. Palin, 44, still in her first term as governor, brings strong conservative credentials — she opposes abortion rights and gay marriage, supports increased domestic drilling for oil, is a lifelong member of the National Rifle Association and has a son in the U.S. Army who deploys to Iraq next month.
"I've spent the last few months looking for a running mate who can best help me shake up Washington and make it start working again for the people that are counting on us," Mr. McCain told 15,000 supporters waving red, white and blue glow sticks in a college basketball arena.
"When you get to know her, you're going to be as impressed as I am," he said. "She's got the grit, integrity, good sense and fierce devotion to the common good that is exactly what we need in Washington today."
For her part, Mrs. Palin, flanked by her husband and four of her five children, was poised at the podium as she stepped into the national spotlight, delivering her speech from a TelePrompTer in a fired-up voice.
"Some of life's greatest opportunities come unexpectedly, and this is definitely the case today," she said with a smile.
"This is a moment when principles and political independence matter a lot more than just the party lines. … This is a moment when great causes can be won and great threats overcome."
The announcement highlighted one of the more exuberant events of the McCain campaign to date, with the crowd clearly excited by the history-making pick. Supporters serenaded Mr. McCain not once, but three times with choruses of "Happy Birthday to You" to mark his 72nd birthday.
But because the McCain campaign kept the selection secret until word leaked out just a couple of hours before the noontime rally, many Republicans were caught flat-footed, unprepared to talk about the mostly unknown governor.
"I dont know much about her," Sen. Kay Bailey Hutchison, a Texas Republican who was mentioned as a potential vice-presidential candidate, told CNN this morning. "I don't know Sarah Palin."
Related story:ANALYSIS: McCain picks Gov. Palin
Cutting into Mr. Obama's momentum less than 12 hours after the Democrat delivered his nomination acceptance speech before 84,000 cheering supporters in Denver, Mr. McCain's choice soothed many skeptical conservatives, who had threatened open revolt as the Republican maverick toyed with the idea of choosing pro-choice candidates such as former Pennsylvania Gov. Tom Ridge or Connecticut Sen. Joe Lieberman, an independent.
Numerous Republicans, including influential conservatives, were buoyant.
Focus on the Family President James Dobson told The Washington Times he now fully supports Mr. McCain, after previously vowing not to support the GOP candidate.
"If flip-flopping is a sin, I'm a sinner," Mr. Dobson said. "As you know, I once said I don't see how I could ever come to support John McCain."
Mr. Dobson praised Mrs. Palin's reform credentials, but social conservatives said they were also excited about her pro-family and pro-life stances. Fiscal conservatives pointed to her support for tax cuts and her opposition to pork-barrel spending as reasons to get excited.
"She is the best possible choice," Eagle Forum President Phyllis Schlafly, longtime leading spokeswoman of the social conservative movement, told The Washington Times. "She's right on all the important ideas."
Paul M. Weyrich, a founder of the modern conservative movement, added, "I must say, I never expected Senator McCain would make this good of a VP appointee. He could not have selected anyone better."
Watch video of Ralph Hallow discussing the Republican convention coming up next week
The Obama campaign, which has had to fend off GOP attacks about its candidate's relative inexperience, immediately went after Mrs. Palin, a one-term mayor of tiny Wasilla, Alaska, before she was eleced governor, on just that score.
House Democratic Caucus Chairman Rahm Emanuel said the choice represented "political panic," and the Obama campaign put out a quick dismissive statement, saying Mrs. Palin had "zero foreign policy experience."
The McCain campaign immediately fired back.
"It is pretty audacious for the Obama campaign to say that Governor Palin is not qualified to be vice president," said McCain spokesman Jill Hazelbaker. "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. … Senator Obama has spent his time in office running for president," she added.
But Mr. McCain's selection of a woman complicates the Democrats' strategy on how hard to attack the Republican ticket.
Shortly after the harsh initial response, Mr. Obama and running mate Sen. Joseph R. Biden Jr. issued a far more measured statement congratulating the Alaska governor.
Mr. Obama, speaking with reporters while touring a bio-diesel plant in Monaca, Pa., called Mrs. Palin a "compelling person" and chided his own staff for the harsh tone of the first response.
"I think that, you know, campaigns start getting these hair triggers," he said. "The statement that Joe and I put out reflects our sentiments."
The GOP ticket now could have stronger appeal to Democratic women voters unhappy at Sen. Hillary Rodham Clinton's loss in the Democratic primary.
Mrs. Clinton in a statement called Mr. McCain's choice "historic."
"While their policies would take America in the wrong direction, Governor Palin will add an important new voice to the debate," she said.
Still, some Democrats insisted that the choice of Mrs. Palin may have handed the election to Mr. Obama.
"This pick takes the experience hit on Obama off the table," said Democratic strategist Liz Chadderdon. "This is done. I am getting out the '04 inaugural gown I didnt get to wear out and sending it to the cleaners."
But Republicans like political strategist Scott Reed called Mrs. Palin an excellent choice for pointing up contrasts with the Democratic ticket.
"Governor Palin has more executive-level experience than Obama and Biden combined," he said.
In making his pick, Mr. McCain passed over several more prominent prospects who had figured in speculation for months — Minnesota Gov. Tim Pawlenty, former Massachusetts Gov. Mitt Romney and former Pennsylvania Gov. Tom Ridge among them.
Mrs. Palin flew overnight to an airport in Ohio near Dayton, and even as she awaited her formal introduction, some aides said they had believed she was at home in Alaska.
• Ralph Z. Hallow reported from Minneapolis, Minn. Christine Bellantoni, reporting from Monaca, Pa., contributed to this report.