At a raucous rally in the swing state of Ohio, McCain said he made his pick after looking for a political partner "who can best help me shake up Washington and make it start working again for the people who are counting on us."
McCain said that Palin was "exactly who I need. She's exactly who this country needs to help us fight the same old Washington politics of me first and country second."
Palin, whose name wasn't on the short list of prospects so heavily discussed publicly in recent weeks, thus became the first woman named to a spot on a Republican ticket. "I am honored," she said as she stood by a beaming McCain in her first few seconds in the national spotlight.
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 picked an older running mate, and a man whom he said at the outset was qualified to be president.
McCain chose Palin, a generation younger than he is, and a governor less than two years, and made no such claim about her readiness to sit in the Oval Office.
Unlike Biden, who attacked McCain sharply in his debut last week, Palin was indirect in her initial attemps 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 McCain beamed. The Arizona senator was a prisoner of war for more than five years in Vietnam.
Palin made an immediate play for support from Democratic women, mentioning that she followed in the footsteps of Geraldine Ferraro, who was the Democratic vice presidential running mate in 1984.
She also referred favorably to Sen. Hillary Rodham Clinton, who drew 18 million votes in her unsuccessful run against Obama for the Democratic nomination.