"I really hope McCain did his homework," said David Frum, a former speechwriter for President Bush. "I cannot stifle a growing sense of unease that he didn't."

A former McCain adviser, Mike Murphy, said Monday that it remains an open question whether "the running mate in a good or bad way becomes a window into the skills of the nominee."

One Republican strategist with close ties to the campaign described the candidate's closest supporters as "keeping their fingers crossed" in hopes that additional information does not force McCain to revisit the decision.

The unease comes as Palin, 44, prepares for her next big public test: a prime-time, nationally televised speech Wednesday to the Republican National Convention.

She no doubt will receive an enthusiastic welcome from delegates and party activists who continued Monday to express unqualified excitement about Palin's presence on the ticket.

As a staunch opponent of abortion, Palin has invigorated religious conservatives and other members of the GOP base who have been cool to McCain's candidacy and reluctant to work for the campaign with the same verve that fueled Bush's 2004 re-election.

And the speech by Palin was shaping up as a dramatic moment in a convention that so far has been muted by the onslaught of Hurricane Gustav.

But while the GOP grass roots remains protective of Palin, the campaign has moved from celebratory mode into a full defensive posture.

Critics also continue to question why McCain, after months of assailing Democratic nominee Barack Obama as lacking foreign policy experience, would tap a running mate who has been governor for less than two years and before that was mayor of Wasilla, population 7,000.

... contd.