DENVER - John McCain kept his vice presidential pick a closely guarded secret hours before the high-stakes announcement Friday as top prospects seemed to drop away and speculation moved to darkhorse candidate Alaska Gov. Sarah Palin.

Two GOP strategists close to the McCain campaign said all indications pointed to Palin, a self-styled "hockey mom" and political reformer. The strategists spoke on condition of anonymity because they were not authorized by the McCain camp to discuss the matter. There was no confirmation from McCain or his advisers.

With an announcement scheduled in Dayton, Ohio, an associate of Minnesota Gov. Tim Pawlenty said the governor had been informed he is not McCain's pick. The official spoke on condition of anonymity because he was not authorized to speak for Pawlenty, who had all but ruled himself out.

"I'm not going to be there. I plan to be at the state fair. You can draw your conclusion from that," Pawlenty said on his weekly call-in radio show on WCCO-AM in Minneapolis. He also called it "a fair assumption" that he will not be McCain's running mate.

Associates close to former Massachusetts Gov. Mitt Romney were saying the same thing, telling The Associated Press that the former presidential candidate had not been offered the job by McCain.

Palin is a first-term governor credited with reforms of her out-of-the-way state. Newly minted Democratic nominee Barack Obama is making an aggressive play for the traditional GOP stronghold and its three electoral votes, and polls show the race close.

At 44, Palin is younger than Obama and, like McCain, she calls herself a maverick.

A Gulfstream IV from Anchorage, Alaska, flew into Middletown Regional Airport in Butler County near Cincinnati about 10:15 p.m. Thursday, said Rich Bevis, airport manager. He said several people came off the plane, including a woman and two teens, but there was no confirmation of who was aboard.

"They were pretty much hustled off. They came right down the ramp, jumped in some vans here and off they went," Bevis said. "It was all hush, hush."

Among the other possible running mates: former Pennsylvania Gov. Tom Ridge, Democrat-turned-independent Sen. Joe Lieberman of Connecticut and former Rep. Rob Portman of Ohio.

The Arizona senator decided on his choice for vice president early Thursday, but the campaign has given no hint on the selection that will be announced on his 72nd birthday. The speculation sent a buzz throughout Denver, where Obama accepted his party's nomination and put Sen. Joe Biden of Delaware on his ticket.

Jill Hazelbaker, McCain's communications director, gave nothing away during an interview on CBS' "The Early Show."

"John McCain is going to make the choice from his heart. He's going to choose someone who can be a partner in governing. He's going to choose someone who brings character and principle to the table and who shares his priorities. And I'm confident that he's going to make a great pick," Hazelbaker said.

Republicans kick off their national nominating convention next week in St. Paul, Minn., and McCain's campaign hopes the announcement of his running mate will stunt any momentum Obama might get from the just-concluded Democratic National Convention.

McCain was mum on the subject Thursday as he and his wife, Cindy, boarded a plane in Phoenix bound for Dayton.