DENVER - John McCain tapped little-known Alaska Gov. Sarah Palin to be his vice presidential running mate, two senior campaign officials told The Associated Press on Friday.

In this July 29, 2008, Associated Press file
photo, Alaska Gov. Sarah Palin speaks to reporters.

A formal announcement was expected within a few hours at a campaign rally in swing-state Ohio.

Palin, 44, is a self-styled hockey mom and political reformer who has been governor of her state less than two years.

Palin's selection was a stunning surprise, as McCain passed over many other better known prospects, some of whom had been the subject of intense speculation for weeks or months.

At 44, she is a generation younger than Sen. Joseph Biden of Delaware, who is Barack Obama's running mate on the Democratic ticket.

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.