PHOENIX, Arizona (CNN) - Sarah Palin's selection as John McCain's running mate redefined how vice-presidential candidates influence a campaign. Unfortunately for McCain, the Alaska governor hurt his presidential bid more than she helped.
Watch: Palin weighs in on 2012
Palin had been unfamiliar to most Americans, aside from some conservative writers and bloggers, who had admired her since she upended Alaska's Republican establishment by knocking off incumbent Gov. Frank Murkowski in 2006.
That all changed on August 29 - the morning after Sen. Barack Obama's acceptance speech at the Democratic National Convention - when Palin was introduced by McCain.
It wasn't just reporters who were stunned. Even McCain staffers at the event itself were shocked. Many assumed McCain would tap a GOP heavyweight like Mitt Romney or Tim Pawlenty. The most daring option, many thought, would be Joe Lieberman, a former Democrat.
But Palin's debut instantly energized the Republican base, which had long been cool to McCain, and the GOP ticket surged in the polls.