But now the magnitude of McCain's gamble is becoming clear.

For every piece of the portrait of Palin that the McCain campaign sketches, a far more complicated picture is drawn.

The youthful mother of five whose placement on the ticket was meant to reinforce traditional values has revealed that her unmarried teenage daughter is pregnant, information that the family and the campaign said they had hoped to keep private.

The woman introduced to America as a reform-minded Washington outsider who opposed the infamous "bridge to nowhere" — the symbol of McCain's hatred of wasteful spending — originally supported its construction. The governor, who in her introductory speech decried the practice of budgetary "earmarks," sought, as the state's chief executive and as mayor of Wasilla, hundreds of millions of dollars in such federal funding for local projects.

Moreover, Palin has retained a lawyer to represent her in a controversy the McCain campaign said it had fully researched -- Palin's role in dismissing a state police official who had refused to fire a trooper who divorced Palin's sister.

On Monday, the McCain campaign dispatched lawyers to Alaska in a move described as an attempt to manage a growing crowd of journalists who have traveled there to inspect Palin's background. But the move raises the impression that the McCain campaign didn't know everything about his No. 2 and is now racing to learn what it can while trying to avoid tough questions about the Arizona senator's decision-making process.

"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.

The campaign has little room for error. A new CBS News poll found that 66 percent of registered voters are undecided about Palin.