ST. PAUL (Reuters) - John McCain wanted to create some buzz with his pick of Sarah Palin as his running mate -- but not this kind of buzz.

In choosing a politically unknown first-term Alaska governor as his No. 2, McCain invited an exploration of her past and her public record -- including an ongoing ethics probe into the firing of a public safety official in Alaska and news that her unmarried teenage daughter is pregnant.

Whether the disclosures are a temporary diversion or early signs of more problems to come, Palin’s flawed roll-in to the Republican convention was a setback for a campaign trying to build momentum for the November 4 showdown with Democratic presidential rival Barack Obama.

“Clearly they would rather not be talking about state trooper investigations and teenage pregnancies right now,” said Dan Schnur, a McCain aide during his 2000 presidential bid who now heads the Jesse Unruh Institute of Politics in California.

The stories raised questions about McCain’s judgment and the depth of investigation that preceded Palin’s selection -- exactly the sort of issues a candidate with a reputation for being impetuous does not need.

It also created a sense of uncertainty about Palin as the national media descends on Alaska to explore her background.

“I think there is significant reason for the campaign and Republicans to worry about what might be coming next,” said Cal Jillson, a political analyst from Southern Methodist University in Dallas.

U.S. Republican Vice-Presidential candidate Governor Sarah Palin (R-AK) (C) and her family members are seen in this 2007 handout photo. REUTERS/State of Alaska/Handout

“They didn’t have time to think about how to frame these issues and deal with them publicly before the selection,” he said.

The McCain campaign disputed reports Palin had not been thoroughly investigated before she was tapped as No. 2.

It released Republican voter registration records to rebut reports she had belonged to the Alaska Independence Party -- which once sought a vote on whether the state should secede.

Many Republicans rallied around Palin after the news of her daughter Bristol’s pregnancy surfaced on Monday, and leading social conservatives dismissed the issue as a private matter and praised the family’s choice to deliver the baby.

‘CHOOSING LIFE’

“Fortunately, Bristol is following her mother and father’s example of choosing life in the midst of a difficult situation,” said Tony Perkins, president of the Family Research Council.

The choice of Palin, 44, a conservative self-described “hockey mom” and mother of five with a record of challenging the state’s party establishment, was aimed at solidifying McCain’s conservative supporters, appealing to independent women voters and enhancing McCain’s own reformer credentials.

But disclosures about the governor’s daughter and coverage of the ethics probe -- which will conclude with a report in late October on whether Palin improperly dismissed a public safety commissioner who would not fire a state trooper who had divorced her sister -- grabbed the political spotlight.

Schnur said her family difficulties could have a positive effect with voters accustomed to family problems. Part of Palin’s appeal is her normal background as a small-town kid who went to a state school, shoots guns and enjoys outdoor sports.

“It’s the sort of thing many people can relate to,” Schnur said. “It is part of her story.”

Given the problems, some questioned why Palin accepted the nomination as vice president, subjecting her family to such scrutiny and taking herself away from her baby born in April.

“Our big concern is when you have both parents working long hours and placing their children in day care from an early age,” said Bill Maier, a vice president at the influential Christian conservative group Focus on the Family.

“But Governor Palin seems to have been able to maintain a balance between work and family.”