In search of V-P candidate, McCain calls Bobby Jindal to his ranch ADAM NAGOURNEY

McCain’s campaign described this as a social weekend that would include 10 couples, and — as has been its policy — declined to discuss any aspect of the vice-presidential search.

Some of McCain’s associates said on Wednesday that while these would not be formal interviews, the weekend would give McCain a chance to get to know some of his potential running mates in a social context. McCain is known as a social and gregarious candidate and Senator, and his associates said personal chemistry would be a crucial consideration in his choice.

The identities of the potential running mates who have been summoned to Sedona are not a surprise. And even encouraging the perception that they are under consideration might be more a matter of appearance than political reality: the mere impression that McCain is considering a running mate from Florida, for example, could help him in a critical state where he campaigned on Wednesday.

Still, the timing — coming as Senator Barack Obama of Illinois appears to have all but nailed down the Democratic nomination — suggested a new focus. McCain, arguably more than most presidential candidates in recent elections, has a lot riding on making a choice for running mate that could provide a boost to his candidacy in a tough atmosphere for Republicans.

In addition to Crist, Jindal and Romney, the McCain guest list includes some of his top political counsellors and at least one senior business executive, Frederick W Smith, the chairman of FedEx.

McCain himself has said his choice of a running mate would draw particular scrutiny from voters given his age; he is now 71. The meeting, which was not disclosed publicly, is taking place on a weekend after McCain releases his health records. The release of those records on Friday is itself a high-profile event that could — by design or not — draw attention away from the gathering.

McCain said this month that he had assembled a list of about 20 potential running mates. He said he had not decided when he would make a decision; his aides made clear that he would keep the process as closely held as possible.

Jindal, who was born in Baton Rouge, Louisiana, to a family that had just arrived there from India, took office in January after serving three years in the House of Representatives. In a race with four candidates, Jindal, who was born a Hindu but converted to Roman Catholicism as a teenager, won 54 per cent of the vote after campaigning as a social conservative, opposing human embryonic stem cell research and abortion, and favouring teaching “intelligent design” in schools as an alternative to evolution. He is considered a rising Republican party star.

Crist, a fairly popular first-term governor, has been included on various lists of potential running mates for McCain, whom he endorsed shortly before Florida’s January primary that effectively helped McCain claim the nomination. Crist said Wednesday that he and McCain had not discussed the prospect, not even at a fundraiser in Miami that the two attended Tuesday night.

The McCain campaign, Crist said, has not solicited the kind of personal information typically requested to vet possible running mates.

As governor of Florida, Crist, 51, would bring obvious assets to the Republican ticket, beginning with his popularity in a state that is almost always an electoral battleground — and where Obama appears to be struggling. Crist’s relative youth could also be an asset for McCain, who has made clear that age will be a consideration in his search for a running mate.

Romney, the former chief executive who ran for the 2008 Republican nomination and who was born in Michigan, has made no secret of his desire to join McCain’s presidential ticket. Romney’s MBA skills and business background — including running the 2002 Salt Lake City Olympic Games — could address concerns about McCain’s ability to manage a struggling economy.