St. Paul - Only four days ago, the nation's voters were asked to accept John McCain's assurances that Sarah Palin, known to only a tiny portion of the public and barely to McCain himself, was fully suited to be vice president.

    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 of the Alaska governor is drawn.

    The youthful mother of five whose placement on the ticket was meant to reinforce traditional values has now revealed that her unmarried teenage daughter is pregnant - a piece of 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 now 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 advisor, Mike Murphy, said Monday that it remained an open question whether "the running mate in a good or bad way becomes a window into the skills of the nominee."

    Most dangerous of all, McCain's team does not seem to know what new development, if any, might grab the public's attention.

    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. According to this Republican, who would discuss internal campaign strategizing only on condition of anonymity, the McCain team used little more than a Google Internet search as part of a rushed effort to review Palin's potential pitfalls. Just over a week ago, Palin was not on McCain's short list of potential running mates, the Republican said.

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

    She will no doubt 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, even in cases of rape or incest, 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 President Bush's 2004 reelection.

    And the speech by Palin is shaping up as a dramatic moment in a convention that has been muted by Hurricane Gustav.

    Although grass-roots Republicans remain protective of Palin, the campaign has clearly moved from celebratory mode into a full defensive posture.

    Critics 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.

    McCain's wife, Cindy, told an interviewer over the weekend that Alaska's proximity to Russia bolstered Palin's credentials, and Palin has pointed to her leadership of the Alaska National Guard and her Army son's imminent service in Iraq as evidence of expertise.

    The campaign has little room for error. A new CBS News poll found that 66% of registered voters were undecided about Palin. And although enthusiastic support from the GOP base is important, strategists know that McCain cannot win without appealing to moderate voters as well - a bloc that the campaign had hoped Palin's middle-class roots would help win over.

    "She remains very popular in the convention hall," said Murphy, "but it's the rest of the country that matters."

    Palin could face questions in on other facets of her past, such as her 1990s membership in the Alaskan Independence Party, a group that has pushed for more than 30 years to give Alaskans a vote on whether to secede from the union.

    Another potentially troublesome story line is Palin's past support for federally funded projects that she now claims to have opposed - a key piece of her reformist image to which McCain was most attracted.

    As mayor of Wasilla, Palin made regular trips to Washington seeking federal aid. The city received $26.9 million in earmarks during her tenure from fiscal year 2000 to 2003, according to the nonpartisan Taxpayers for Common Sense, which tracks pork barrel spending.

    As The Times reported Monday, Palin has requested 31 earmarks in next year's federal budget worth about $197 million. On Friday, she portrayed herself as a champion of curbing the "abuses" of earmark spending.

    For McCain, the Friday surprise of introducing Palin resulted in a weekend of buzz and anticipation. But if additional surprises surface about Palin, McCain could face stark choices.

    Might he be forced to anger conservatives by dumping Palin? Could he risk an admission of poor judgment, tainting what he has long claimed as a key strength?

    And if a new stumbling block could have been discovered by a more careful search, critics will no doubt question a well-known trait of McCain's: that he sometimes makes decisions on emotion instead of careful deliberation.

    "John McCain is decisive and listens mainly to John McCain," said David Keene, head of the American Conservative Union.

    "That is either comforting or discomforting, depending on whether you're trying to get him to do what you want."

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    Times staff writers Doyle McManus, Tom Hamburger, James Rainey and Maeve Reston contributed to this report.