John McCain has tapped little-known Alaska Gov. Sarah Palin to be his running mate on the eve of the Republican National Convention.

In an announcement, the campaign says that Palin, who has been governor less than two years, "has the record of reform and bipartisanship that others can only speak of."

The campaign goes on to say: "Her experience in shaking up the status quo is exactly what is needed in Washington today."

McCain introduced his running-mate at a rally in Ohio.

Palin is a self-styled hockey mom and political reformer. She is a conservative with a maverick streak who has shown a willingness to clash with others in her own party.

The 44-year-old Palin is a former mayor of Wasilla who became governor in December 2006. She has a national reputation for bucking her party's establishment and Alaska's powerful oil industry.

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

She and her husband, Todd Palin, have five children. The latest was born last April with Down syndrome.

The Palins have said there was never any doubt they would have the child, after learning in the fourth month of pregnancy that the boy had Down syndrome. Palin said: "We've both been very vocal about being pro-life."

She was chosen over several more prominent prospects including Minnesota Gov. Tim Pawlenty, former Massachusetts Gov. Mitt Romney and former Pennsylvania Gov. Tom Ridge.