1. Charlie Crist The popular governor of Florida would be a massive boost to McCain's chances of taking the state, a key battleground with 27 electoral votes on offer. At 51, his youth could counteract concerns about McCain's advanced years, while his shock of dazzling white hair and permatan make him both telegenic and instantly recognisable. Florida's attorney-general before becoming governor in 2006, he has a reputation as a hardliner on law and order, while his strong conservative credentials on issues such as gun rights, abortion and marriage could help shore up the Republican right. Crist was invited to a gathering at McCain's Arizona ranch along with a handful of other VP hopefuls last month, and has recently appeared alongside the nominee at Florida campaign stops.
Follow the money: 8/1
2. Tim Pawlenty Again, the governor of a key battleground - this time Minnesota. The state offers fewer electoral votes that Florida, but rival Barack Obama is performing far better here in the polls, with a comfortable lead that McCain needs to peg back. Pawlenty has solid conservative credentials which could help win over right-wingers alienated by McCain's moderate stance on issues such as immigration and civil unions. McCain aides have suggested Pawlenty is near the top of the shortlist - I would have made him number one had he been invited to the nominee's Arizona "audition". However his absence could simply indicate that he is the man to beat.
Follow the money: 6/1
3. Bobby Jindal This rising star took over as governor of Louisiana in January, becoming the first American of South Asian origin to be hold such office. A staunch social conservative, he opposes human embryonic stem cell research and abortion in any form, and favours the teaching of intelligent design in schools as an alternative to evolution - positions that could help win over the religious right. At 36, he is considered by some to be too young for the VP spot, but has been widely tipped as a favourite and was one of the favoured few at the Arizona gathering. He has also appeared alongside McCain at recent campaign stops in Louisiana.
Follow the money: 6/1
4. Mitt Romney Rumours of animosity between Romney and McCain have led some to discount this former Massachussetts governor, but he remains a strong all-round contender. A former opponent in the nomination race, his solid conservative credentials proved a big draw for right-wingers , while his business experience as head of private equity investment firm Bain Capital and CEO of the 2002 Winter Olympics in Salt Lake City would assuage concerns over McCain's ability to manage a struggling economy. Fears that his Mormonism could harm him among Christian evangelicals do not seem to overly bother McCain, who invited Romney to his gathering of VP favourites.
Follow the money: 5/1
5. Mike Huckabee A Baptist pastor with huge appeal to the religious right - a group with whom McCain has severe difficulties - Huckabee staked his claim to the VP spot when he took a swathe of southern states during the primaries. But his staunchly conservative views on religious and social issues - he does not believe in evolution, for example - were not mirrored by a hardline stance on economic matters during his ten-year stint as governor of Arkansas. He does however have a certain amount of charisma - or perhaps quirk appeal - having made regular campaign appearances with his Christian rock band Capitol Offense. Huckabee received an invitation to McCain's ranch - but did not attend.
Follow the money: 10/1
6. Tom Coburn A rock-solid conservative, Coburn's tough stance on issues such as immigration could allay concerns about McCain's liberal voting record. The pair have similar views on fiscal conservatism, a matter on which they have worked together before. However he is not particularly charismatic and as a senator represents Oklahoma, which is not expected to be a battleground state this year.
Follow the money: 25/1
7. Condoleezza Rice Her strong national security credentials - she was National Security Advisor to President Bush before taking over from Colin Powell as Secretary of State - will appeal to McCain. Meanwhile her status as a black woman could go some way towards negating the Obama factor and attracting women voters, including disgruntled supporters of Hillary Clinton. Considered a conservative Republican, she could also bring those in the party who are disenchanted with McCain back into the fold.
Follow the money: 14/1
8. Sarah Palin The telegenic governor of Alaska has a down-to-earth persona which would appeal to rural Americans. At 44, she is energetic and devoted to her family, which could help win over the soccer mom crowd. Her life-long membership of the National Rifle Association would make her immensely popular with the gun lobby, while she also has strong credentials as a social conservative. Known for her maverick governing style, McCain could see in her something of a kindred spirit.
Follow the money: 6/1
9. Mark Sanford The governor of South Carolina is youthful enough, at 48, and conservative enough, with a lifetime rating of 92/100 from the American Conservative Union, to provide a good counterbalance to McCain. His early support helped the Arizona senator to a primary win in the state, while his Southern appeal could pull in voters there. But some argue that McCain should have little difficulty in the South regardless of his running mate, while concerns have been raised over his lack of name recognition.
Follow the money: 12/1
10. Joe Lieberman If there's anyone to whom McCain owes the VP spot, it is Joe Lieberman. An Democrat-turned-independent, sometimes described as an Independent Democrat, Lieberman crossed party lines to throw his full weight behind McCain early in the primary season. Since then the pair have often seemed inseparable, and on many aspects of policy there is certainly little distance between them, particularly when it comes to defence and foreign policy. Far from being a strength, however, this could prove Lieberman's greatest drawback. As an independent he might burnish McCain's appeal to swing voters, but his selection would certainly not help - and could well harm - the nominee's efforts to woo conservative Republicans.
Follow the money: 20/1