St Paul, Minnesota - Until Friday, few had ever heard of Sarah Palin, the Republican governor of Alaska.

But within 48 hours after Republican Senator John McCain named her his vice presidential running mate, the country's intense media spotlight was at work trying to find out who she was.

First, there was the matter of an ongoing investigation in Alaska after she fired her public safety commissioner amidst his refusal to fire her brother-in-law. She claimed the man, who was a state trooper in the midst of a messy divorce from her sister, had threatened her family.

The results of the probe into whether she unduly used her power to influence a family matter are to be released in October, before the November 4 elections, when McCain will face Democratic nominee Barack Obama. Palin has reportedly hired a lawyer to represent her during the probe.

Then, on Monday, news of the pregnancy of Palin's 17-year-old daughter, Bristol, leapt into the headlines.

This - while the McCain campaign was trying to tone down partisan politics at its all-important nominating convention in St Paul, Minnesota out of respect for the major natural disaster of Hurricane Gustav unfolding on the country's southern coast.

Yet the story of Bristol's pregnancy and her mother's opposition to sex education in school and advocacy of abstinence quickly commanded attention.

Responding to internet rumours about her daughter, Palin and her husband Todd issued a statement confirming that their daughter Bristol was five months pregnant.

"Our beautiful daughter Bristol came to us with news that as parents we knew would make her grow up faster than we had ever planned," the couple said.

"We're proud of Bristol's decision to have her baby and even prouder to become grandparents."

The Palins said that Bristol and "the young man (Levi) she will marry are going to realize very quickly the difficulties of raising a child, which is why they will have the love and support of our entire family."

Palin, a mother of five, is an outspoken opponent of abortion, and her choice by McCain was seen as a pitch to conservative Republicans uneasy about the nomination of the more centrist senator.

The Palins asked the media to respect their family's privacy.

Although Palin's lack of national experience has been criticized by Democrats, Obama drew the line Monday about jumping into the fray over the daughter's pregnancy.

"I have said this before and I will repeat again. I believe people's families are off limits. People's children are especially off limits," he told reporters in broadcast remarks. "This should not be part of our politics."

Obama noted that his mother was only 18 when he was born.

He energetically refuted that his campaign was involved in internet rumours that Bristol was in fact the mother of Palin's four- month-old baby, Trig, who suffers Down's Syndrome.

"Our people were not involved in any way in this. If I ever thought someone in my campaign was involved in something like that they'd be fired," Obama said.

Bristol carried the baby during Friday's vice presidential announcement.

Critics were raising questions about McCain's judgement in selecting Palin as his vice presidential candidate, and wondered about Palin's judgement in accepting the offer when she knew her child would be subjected to the media spotlight.

McCain's spokesman Tucker Bounds said that McCain knew about both issues - the investigation into Palin as well as Bristol's pregnancy - before naming her his running mate.

One Alaska state senator, asked by CNN what he thought about the pregnancy issue, said the situation only showed that Palin was human.

Bounds defended Palin's executive and foreign experience, saying she had commanded Alaska's national guard during her two years as governor. (dpa)