ST. PAUL, Minn. — The announcement yesterday by Alaska Gov. Sarah Palin and her husband that their 17-year-old daughter is pregnant out of wedlock raised new questions about how thoroughly John McCain investigated the background of his vice-presidential pick.

Whether the 72-year-old McCain's selection of 44-year-old Palin as his running mate was carefully considered or impulsive is a matter of growing interest.

McCain campaign officials said the Palin family's statement was prompted in part by a spate of Internet rumors suggesting that Bristol Palin was actually the mother of Sarah Palin's 4-month son, Trig. They denounced the rumors and went on the offensive yesterday morning when the news of Bristol Palin's pregnancy surfaced.

McCain advisers said he knew about the pregnancy before he settled on Palin, and said Palin had been thoroughly vetted.

Before she was chosen to be McCain's running mate, Palin submitted to a three-hour interview with the head of his vice presidential search team, and responded to a 70-question form that included "intrusive personal questions," a senior campaign aide said yesterday.

In Alaska, however, there's little evidence of a thorough vetting process.

While it's possible that some people in Alaska were called during the process, there was no sign of it. The former U.S. attorney for Alaska, Wev Shea, who enthusiastically recommended Palin back in March, said he was never contacted with any follow-up questions.

Chris Coleman, one of Palin's next-door neighbors, said no one representing McCain spoke to him about Palin. Another neighbor also was never contacted, he said yesterday.

Republican Gail Phillips, a former speaker of the Alaska House, said she was shocked by McCain's selection of Palin and told her husband, Walt, "This can't be happening because his advance team didn't come to Alaska to check her out." She said she would've heard had someone been poking around.

"We're not a very big state," Phillips said. "People I talk to would've heard something."

Walt Monegan, the commissioner of public safety whom Palin fired in July, said no one from the McCain campaign contacted him, either. His firing is now the subject of a special legislative investigation into whether Palin or members of her administration improperly interfered with the running of his department by pushing for dismissal of a state trooper involved in a divorce and custody battle with Palin's sister.

The FBI declined to say whether it conducted a full-field investigation of Palin's background before McCain tapped her as his running mate. FBI spokesman Richard Kolko referred callers to the McCain campaign.

Previous vice-presidential picks — even those with long records in national politics — have come under much closer scrutiny. In 2000, Democratic nominee Al Gore picked Joe Lieberman after a vetting process that lasted about 10 months, including poring through some 800 legal opinions Lieberman had been involved with as Connecticut attorney general.

Rick Davis, McCain's campaign manager, was asked yesterday as he walked through the Xcel Energy Center in St. Paul if he was satisfied with Palin's vetting. "I'm not gonna get into that," he said.

As their national convention got under way yesterday, Republicans stood by Palin and tried to make the media coverage, rather than McCain's decision-making, the issue.

"We're asking the media to respect a person's privacy," said Maria Comella, Palin's campaign spokesman.

A McCain adviser, Douglas Holt-Eakin, called the Palin pregnancy a family matter "best left to them."

McCain's Democratic opponent, Barack Obama, said the reports about Palin's daughter's pregnancy have no relevance to Palin's potential performance as vice president.

"You know, my mother had me when she was 18," Obama said. "And how family deals with issues and teenage children, that shouldn't be the topic of our politics, and I hope that anybody who is supporting me understands that is off-limits."

Delegates to the Republican convention said the pregnancy should have no impact on the McCain campaign. Ralph Seekins, an Alaska delegate, said families would identify with the challenges the Palins face.

"I'm proud of their daughter having to do the right thing. A lot of people would just say 'get rid of that problem,' " Seekins said. "My family's not perfect. I don't know anybody's that is. I've not even been perfect in my own life. I think people are going to understand that, even from a political standpoint."

However, Sherry Whistine, a Republican conservative blogger from Palin's home area of Wasilla, said that she can't believe how Palin could accept the nomination knowing that doing so would shine a spotlight on her daughter.

"What kind of woman, knowing all of this, knowing this is happening, would put her children in the position where the whole world, the whole nation, is going to see the uglies?" she said.

The Washington Post contributed to this report.