FAIRBORN, Ohio -- In a surprise pick that may have been aimed at Democrats disgruntled over Sen. Hillary Rodham Clinton's defeat, Sen. John McCain today named 44-year-old Gov. Sarah Palin of Alaska as his running mate.

Ms. Palin, the first woman and youngest governor of the 49th state, would become the first woman vice presidential nominee in the history of the Republican Party. She will accept the party's nomination Wednesday night in St. Paul, Minn.

"She's not from these parts and she's not from Washington, but when you get to know her, you're going to be as impressed as I am,'' Mr. McCain said. "She's got grit, integrity, good sense, and fierce devotion to the common good and what is right, and that is exactly what we need in Washington today."

The popular first-term governor and mother of five plays into the "maverick" and reformer image that Mr. McCain has tried to foster in an attempt to distance himself from the unpopular President Bush.

Ms. Palin has a reputation for bucking her party, riding GOP ethics scandal to a primary victory over a Republican incumbent governor and then defeating her Democratic opponent in 2006. An abortion rights opponent, she gave birth to her fifth child in April.

Her oldest son will soon be deployed to Iraq with his U.S. Army brigade.

"As the mother of one of those soldiers and as commander of the Alaska National Guard, that's the kind of man that I want as our commander-in-chief," she said of Mr. McCain.

Born in Idaho, she was transplanted to Alaska as a child and earned the nickname "Sarah Barracuda"' as a player on her high school basketball team. She was a Miss Alaska runner-up in 1984. She hunts, fishes, rides snowmobiles, and is a member of the National Rifle Association.

"She knows where she comes from and she knows who she works for," Mr. McCain. "She stands up for what is right and she doesn't let anybody tell her to sit down."

The Obama campaign immediately attacked her level of experience.

"Today, John McCain put the former mayor of a town of 9,000 with zero foreign policy experience a heartbeat away from the presidency," said Obama campaign spokesman Bill Burton. "Gov. 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."

She is already at odds with Mr. McCain on one issue, oil exploration in the Arctic National Wildlife Refuge. She favors it.

While Mr. McCain has adamantly supported more off-shore drilling, he has so far kept ANWR off the table and he succeeded in keeping an endorsement of ANWR drilling out of the draft party platform that will come to a vote next week at the convention in St. Paul, Minn.

Mr. McCain has attempted to exploit the reluctance of some Clinton supporters to rally behind Barack Obama after he secured his party's nomination.

Democrats tried to heal the wounds with their convention this week, culminating with robust endorsements of Mr. Obama from Mrs. Clinton and former President Bill Clinton. But it remains to be seen how many of those who voted for her will follow her to Mr. Obama on Nov. 4.

In a direct nod to Mrs. Clinton and this week's suggestion that her votes reflected 18 million cracks in the glass ceiling for women, Ms. Palin said, "The women of America are not finished yet, and we can shatter that glass ceiling."

She also acknowledged the first woman vice presidential candidate of a major party -- Geraldine Ferraro, Walter Mondale's running mate on the failed Democratic ticket in 1988.

Mr. McCain made the announcement on his 72nd birthday, within hours of Mr. Obama's acceptance speech in Denver in hopes of stepping on any momentum the Democrat may have enjoyed just as Republicans start their own convention.

The road to St. Paul will take Mr. McCain and Ms. Palin to another battleground state, Pennsylvania, on Saturday and then to Toledo on Labor Day.

Ms. Palin had come up early on in the vice presidential search, but most speculation had focused on former rival and Massachusetts Gov. Mitt Romney and on Minnesota Gov. Tim Pawlenty. But then an overnight private flight from Anchorage, Alaska, landed at a nearby airport.

Others considered included former Pennsylvania Gov. Tom Ridge, Texas Sen. Kay Bailey Hutchison, and Independent Connecticut Sen. Joe Lieberman.

In addition to being Mr. McCain's birthday, Friday marked the 20th anniversary for Gov. Palin and her husband, Todd, who works in the Alaskan oil fields.

"I promised Todd a little anniversary present, and hopefully he knows I did deliver," she said.

Tricia Bowcher of Maineville, about an hour from Dayton, attended the rally at the Ervin J. Nutter Center on the campus of Wright State University. The crowd numbered more than 10,000, huge compared to what Mr. McCain had been drawing on the stump. Democrats claimed the McCain campaign had to bus people in from Indiana to fill the seats, a contention Ohio Republican Party Deputy Chairman Kevin DeWine dismissed.

If Mr. McCain were intent on picking a woman, Ms. Bowcher said she would have preferred Ms. Hutchison.

"She's more experienced that what this woman is," she said. "To be honest, I would have preferred Mitt Romney over everyone really, because he's conservative and just embodies the Republican base.''

Still, she said she trusts Mr. McCain's judgment and would have supported him on Nov. 4 regardless of who he picked.