DAYTON, Ohio - 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."

"I am honored," she said moments later, the first Republican woman chosen for national office.

Palin has built her political career in large measure by taking on fellow Republicans.

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.

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.

White House aides said President Bush called Palin to congratulate her and wish her luck. He told her 'the McCain-Palin ticket is very strong' and said he looked forward to their winning in November, said press secretary Dana Perino.

"The White House is enthused and excited about this choice," she said.

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.