In an election campaign notable for its surprises, Sarah Palin, the Republican vice- presidential candidate, may be about to spring a new one — the wedding of her pregnant teenage daughter to her ice-hockey-playing fiancé before the November 4 election.

Inside John McCain’s campaign the expectation is growing that there will be a popularity boosting pre-election wedding in Alaska between Bristol Palin, 17, and Levi Johnston, 18, her schoolmate and father of her baby. “It would be fantastic,” said a McCain insider. “You would have every TV camera there. The entire country would be watching. It would shut down the race for a week.”

There is already some urgency to the wedding as Bristol, who is six months pregnant, may not want to walk down the aisle too close to her date of delivery. She turns 18 on October 18, a respectable age for a bride — and the same age as Barack Obama’s pregnant mother when she married his Kenyan father. The Democrat has already declared Bristol’s private life off-limits as far as his campaign is concerned.

The selection of Palin, 44, the moose-hunting governor of Alaska, as his running mate was one of McCain’s biggest gambles. It paid off handsomely at first, but she could benefit from a fresh injection of homespun authenticity, the hallmark of her style, provided by her daughter’s wedding after appearing out of depth away from her home state.

David Letterman, the late-night television chat show host, joked that Palin’s meetings with world leaders at the United Nations in New York looked like “take your daughter to work day”.

In a series of heavily criticised interviews with Katie Couric of CBS News, she fumbled her points about Alaska’s proximity to Russia and sounded like an over-crammed, under-informed student. Palin was stumped when Couric asked her to provide examples of McCain’s proposals for reforming the banking industry. “I’ll try to find some and I’ll bring them to you,” she said eventually. Republicans are quailing in advance of one of her biggest tests of the election, her televised debate with Joe Biden, the Democratic vice-presidential nominee, on Thursday in St Louis, Missouri.

The conservative commentator Kathleen Parker, an early admirer, shocked McCain supporters late last week by calling on Palin to withdraw. “My cringe reflex is exhausted,” she wrote in National Review Online, a conservative journal. “Palin’s recent interviews . . . all revealed an attractive, earnest, confident candidate. Who Is Clearly Out of Her League.”

Parker advised Palin to “save McCain, her party and the country she loves” by announcing that she wanted to spend more time with Trig, her five-month-old Down’s syndrome baby: “No one would criticise a mother who puts her family first.”

The Republicans’ Palin “bounce” ended last week as concern for the plunging economy mounted. Obama ended the week four points ahead of McCain on 48% to 44% in the RealClearPolitics poll of polls. A Rasmussen survey showed that McCain’s lead among white women voters slipped to two points, as opposed to 14 points for George W Bush in 2004.

However, Palin has a remarkable ability to galvanise the evangelical voters and social conservatives who form the Republican base. The party boasted last week that it will probably surpass its fundraising goal of $100m for September and October. Much of it is because of the grassroots enthusiasm for Palin, boosted by her decision to have Trig and to support her pregnant daughter.

McCain is expected to have a front-row seat at Bristol’s wedding and to benefit from the outpouring of goodwill that it could bring. “What’s the downside?” a source inside the McCain campaign said. “It would be wonderful. I don’t know that there has ever been a pre-election wedding before.”

When McCain picked Palin as his running mate, Bristol’s pregnancy was regarded as a potential liability with voters. The idea was to keep her condition quiet initially. However, rumours quickly surfaced that Trig was Bristol’s son. News that Bristol was pregnant, making it a near-biological impossibility for her to be Trig’s mother, had to be rushed out.

Johnston was greeted with a handshake and friendly slap on the back by McCain in St Paul, Minnesota, and treated as a member of the family during the Republican national convention when he appeared on stage after Palin’s speech.

The ice-hockey player wrote on his MySpace page he was a “f****** redneck” and stated, “I don’t want kids.” But a McCain insider predicted he would marry Bristol whenever his future mother-in-law wanted. “It’s a shotgun wedding. She kills things,” the source joked.

The McCain campaign is divided over how to handle Palin’s appearances, which have been so limited and over-rehearsed that last week Campbell Brown, a CNN anchor, accused it of sexism. “Stop treating Sarah Palin like she is a delicate flower who will wilt at any moment,” she said. “If she were a man, would we be putting up with this? . . . Would she be coddled this way, cloistered this way? I don’t think so.”

Inside McCain’s camp, aides are arguing over the benefits of “letting Sarah be Sarah”. Some officials believe her appeal to voters is such that it would be worth risking a few gaffes in exchange for letting her personality shine through.

The question will assume particular importance when she faces Biden, 65, in debate. The chairman of the Senate foreign relations committee has already come up with a multitude of gaffes, from asking a wheelchair-bound man to stand up at one of his rallies to admitting that Hillary Clinton “might have been a better pick” for vice-president, without any seeming ill-effect.

McCain officials believe that Palin’s underdog status gives her a chance to shine. “Joe Biden is going to have to destroy her for it to be perceived as a victory for him,” said an aide.

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