DAYTON (AP) — John McCain picked Alaska Gov. Sarah Palin, a maverick conservative with less than two years in office, as his vice presidential running mate Friday in a startling choice as the Republican National Convention drew near.

At a raucous rally in the swing state of Ohio, McCain introduced Palin as the political partner "who can best help me shake up Washington and make it start working again for the people who are counting on us."

Palin, the first Republican woman tapped for national office, promised: "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."

"... Politics isn't just a game of competing interests and clashing parties," added the woman who has built her career in large measure by challenging fellow Republicans. "The people of America expect us to seek public office and to serve for the right reasons."

In a fast-developing presidential campaign, McCain made his selection six days after his Democratic rival, Barack Obama, named Sen. Joseph Biden of Delaware, as his running mate.

The contrast between the two announcements was remarkable — Obama, 47, picked a 65-year-old running mate with long experience in government and a man whom he said was qualified to be president.

On his 72nd birthday, McCain chose a 44-year-old running mate who until recently was the mayor of small-town Wasilla, Alaska — and made no claim she was ready to sit in the Oval Office.

His campaign issued a statement saying she was, but even so, it wasn't a point lost on Obama's campaign.

"Today, John McCain put the former mayor of a town of 9,000 with zero foreign policy experience a heartbeat away from the presidency," Adrianne Marsh, a spokeswoman for Obama, said in a written statement.

Unlike Biden, who attacked McCain sharply in his debut last week, Palin was indirect in her initial attempts to elevate McCain over Obama.

"There is only one candidate who has truly fought for America and that man is John McCain," she said as the Arizona senator beamed. McCain was a prisoner of war for more than five years in Vietnam.

McCain trails Obama in the polls among women voters, and Palin moved quickly to remedy that.

She mentioned that she followed in the footsteps of Geraldine Ferraro, who was the Democratic vice presidential running mate in 1984, and referred favorably to Sen. Hillary Rodham Clinton, who drew 18 million votes in her unsuccessful run against Obama for the Democratic nomination.

"But it turns out the women of America aren't finished yet and we can shatter that glass ceiling once and for all," she said.

Republicans said that McCain hoped to blunt Obama's message of political change with his pick, and it appeared likely she could remove all doubt about her home state in the fall campaign.

Obama has targeted Alaska and its three electoral votes, one of several he hoped to turn competitive in the fall despite its long tradition of voting Republican.

Palin has a strong anti-abortion record, and her selection was praised warmly by social conservatives whose support McCain needs to prevail in the campaign for the White House.

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."

"It's an absolutely brilliant choice," said Mathew Staver, dean of Liberty University School of Law. "This will absolutely energize McCain's campaign and energize conservatives," he predicted.

With his pick, McCain passed over more prominent contenders like Minnesota Gov. Tim Pawlenty, as well as others such as former Pennsylvania Gov. Tom Ridge, whose support for abortion rights might have sparked unrest at the convention that opens Monday in St. Paul, Minn.

The timing of McCain's selection appeared designed to limit any political gain Obama derives from his own convention, which ended Thursday night with his nominating acceptance speech before an estimated 84,000 in Invesco Field in Colorado.

Public opinion polls show a close race between Obama and McCain, and with scarcely two months remaining until the election, neither contender can allow the other to jump out to a big post-convention lead.

At 44, she is younger than two of McCain's seven children.

She is three years Obama's junior, as well — and McCain has made much in recent weeks of Obama's relative lack of experience in foreign policy and defense matters.

In its formal announcement, the campaign pointed to her powers as head of the Alaska National Guard and the mother of a soldier herself as evidence that she "understands what it takes to lead our nation..."

McCain has had months to consider his choice, and has made it clear to reporters that one of his overriding goals was to avoid a situation like 1988, when little known Sen. Dan Quayle was thrown into a national campaign with little preparation.

A self-styled hockey mom and political reformer, Palin was mayor of Wasilla, Alaska, population 6,500, until she became governor.

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.

She became governor of her state in December, 2006 after ousting a governor of her own party in a primary and then dispatching a former governor in the general election.

More recently, she has come under the scrutiny of an investigation by the Republican-controlled legislature into the possibility that she ordered the dismissal of Alaska's public safety commissioner because he would not fire her former brother-in-law as a state trooper.

Palin has a long history of run-ins with the Alaska GOP hierarchy, giving her genuine maverick status and reformer credentials that could complement McCain's image.

Two years ago, she ousted the state's Republican incumbent governor, Frank Murkowski in the primary, despite having little money and little establishment backing.

She has also distanced herself from two senior Republican office-holders, Sen. Ted Stevens and Rep. Don young. Both men are under federal corruption investigations.

She had earned stripes — and enmity — after Murkowski made her head of the Alaska Oil and Gas Conservation Commission. From that post, she exposed ethical violations by the state GOP chairman, also a fellow commissioner.

Her husband, Todd Palin, 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 couple lives in Wasilla. They have five children, the youngest of whom was born in April with Down syndrome.

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Associated Press Writer Liz Sidoti reported for this story from Denver.