John McCain was yesterday seeking to steer a Republican convention, already blown off course by Hurricane Gustav, away from the treacherous seas swirling around his running-mate.

Sarah Palin, having galvanised conservative activists and reinvigorated the Republican campaign when she was unveiled as the vice presidential nominee last week, is now the focus of intense public scrutiny while being cited by Democrats as evidence of Mr McCain's poor judgement.

Knowing that the address she delivers at the convention on Wednesday may prove pivotal in the presidential race, she has - aside from a sisterly visit by Laura Bush and Cindy McCain yesterday — spent the past 48 hours out of sight “working on her speech”.

But her name has never been far from the headlines. At first rumours, then disclosures, about her family have reverberated around the country even as pundits question if she has the experience needed for the job.

After an opening day almost wiped out by the hurricane and overshadowed by the clouds gathering over Mrs Palin, the convention returned to a more normal schedule last night with President Bush addressing delegates via a satellite-link.

He told them that Mr McCain was “ready to lead this nation”, not least because the Republican nominee understood that the lesson of 9/11 was to “stay on the offence, stop attacks before they happen, and not wait to be hit again”.

There was also an important speech from Senator Joe Lieberman, the former Democratic vice-presidential nominee, who has switched sides to back Mr McCain because “country matters more than party”.

Mr McCain is said to have wanted Mr Lieberman as his running mate before encountering entrenched opposition from conservatives who had given warning that up to a dozen state delegations might walk out of the convention.

Even so, the choice of Mrs Palin was unexpected and — despite Mr McCain insisting yesterday that “the vetting process was completely thorough” — it is apparent his campaign had time for only a cursory examination of her credentials.

It has since had to make a series of disclosures, including an acknowledgement that her unmarried teenage daughter is five months pregnant. Tucker Eskew, Mrs Palin’s media minder, has admitted that he used Monday’s hurricane as cover to “flush the toilet” by releasing such information to the press.

Although Barack Obama has declined to comment on Mrs Palin’s family life, he has wasted few opportunities to scorn her experience. Yesterday he pointed out that 18 months ago she was merely a mayor, adding: “Governor Palin’s town, Wasilla, has I think 50 employees.”

Yesterday Mr McCain's began fighting back, insisting he was “very proud” of his running mate. The campaign’s senior adviser, Carly Fiorina, denounced Mr Obama for trying to “belittle Sarah Palin’s experience”, adding: “American women are more highly tuned than ever to recognise and decry sexism in all its forms.”

Rudy Giuliani, the former New York mayor, turned on a reporter who asked if Mrs Palin’s family problems would be an issue at the convention, saying: “Frankly, you should be ashamed of yourself. It doesn’t have the slightest relationship to a presidential campaign.”

Mr McCain’s team says that Mrs Palin helps them connect with ordinary voters and that her “Everywoman” story is snatching back attention from Mr Obama. They dismiss suggestions that, in the party of “family values”, this mother-of-five should be at home looking after new Down’s syndrome baby rather than exposing her pregnant daughter to the glare of publicity.

Instead, the religious Right is rallying to her defence. “Families get in trouble all the time,” said Rick Scarborough, the founder of Vision America. “From what I see this family is dealing with it honourably. They are going to carry this baby to a full term as a further testimony of their commitment to life.”

But, in the bars around the twin cities of Minneapolis-St Paul this week, Republicans make whispered references to Harriet Miers, who was nominated by Mr Bush for the Supreme Court before being dropped amid widespread ridicule of her expertise. Some are even mentioning Tom Eagleton, who was thrown off the 1972 Democratic Party presidential ticket after it was revealed that he had been treated for psychiatric problems.

Republican strategist Mike Murphy said that Mrs Palin may yet prove to be the pick who appeals mostly to conservative Republicans. And he added: “If a few more things pop up, the question won’t be her, it’ll be the McCain vetting process.”

Times Recommends

• The Japanese Prime Minister is doomed: or is he?
• Brighton company 'involved in cyber attack'
• The art of survival: it’s all in the mind