By The Associated Press

DENVER — Barack Obama’s spokesman fired off a fast criticism of Republican John McCain’s new running mate on Friday, but the Democratic candidate himself quickly stepped in to offer her congratulations and praise.

Obama, who is eager to win over female voters who backed his rival Hillary Rodham Clinton in the primaries, blamed the mixed messages about McCain’s choice, Alaska Gov. Sarah Palin, on campaign aides with a “hair trigger.”

McCain made his surprise announcement moments before Obama flew from Denver with his running mate, Joe Biden, and their wives. Fresh off his nomination acceptance speech before 84,000 people Thursday night, Obama joined Biden on a three-day bus tour of crucial industrial states that began with a visit to a biodiesel fuel plant in western Pennsylvania.

As the plane was lifting off from Denver, Obama campaign spokesman Bill Burton issued a statement calling Palin an abortion-rights opponent and “the former mayor of a town of 9,000 with zero foreign policy experience.”

Soon thereafter, with the plane over the Midwest, a spokeswoman gave reporters on board a much kinder statement from Biden and Obama.

“Her selection is yet another encouraging sign that old barriers are falling in our politics,” their statement said. “While we obviously have differences over how best to lead this country forward, Gov. Palin is an admirable person and will add a compelling new voice to this campaign.”

After touring the steamy biodiesel fuel plant, Obama offered reporters another comment on Palin.

He has not met her, he said, but “she seems like a compelling person. Obviously a terrific story, personal story. And I’m sure that she will help make the case for the Republicans. Unfortunately, the case is more of the same,” an allusion to his theme that McCain will continue Bush administration policies.

Palin’s selection, Obama said, “is one more indicator of this country moving forward. The fact that you’ve got a woman” as the “vice presidential nominee of one of the major parties, I think, is one more hit against that glass ceiling.”

Clinton often says she made “18 million cracks in the glass ceiling,” a reference to the number of votes she won in primaries as she sought to become the nation’s first female president.

Asked why Burton’s statement had been far more critical of Palin, Obama said, “I think, you know, campaigns start getting these hair triggers. And the statement that Joe and I put out reflects our sentiments.”