Republican presidential hopeful John McCain faces a tough choice over whether to burnish his conservative credentials or boost his appeal among independent voters when he settles on a vice presidential pick later this week. ( dpa )
It is a difficult balancing act for McCain who, if he hopes to be successful in November, must keep his distance from an unpopular Republican administration without alienating the party's conservative base.
McCain, 71, has long had a reputation as a "maverick" within the Republican Party, supporting action on campaign finance reform, immigration, tackling global warming and opposing torture. But those stands, as well as his lukewarm advocacy for social policies, have made him appear suspicious to some conservatives.
A Vietnam War veteran who was held in captivity for five years, McCain has relied mostly on his foreign policy and military credentials in the campaign so far.
Picking a candidate with an economic background could improve McCain's chances as the country flirts with a recession. However, Democratic rival Barack Obama's choice of Senator Joe Biden, a leading voice on foreign policy, could require McCain to go with a security pick after all.
McCain and his running mate will accept the party nomination at next week's Republican convention in St Paul, Minnesota. Some of the leading contenders to join the ticket include:
Mitt Romney, a businessman and former governor of Massachusetts, came closest to claiming the Republican Party mantle from McCain in the primaries. Romney has a proven ability to run a company and a state - two qualities McCain lacks, and which could be crucial in convincing voters that he can manage the economy.
Romney, 51, brings a mix of conservative and moderate credentials that have made both sides suspicious of his true ideology. As a successful two-term governor of left-leaning Massachusetts, Romney supported limited abortion rights for women - a no-no for conservative Republicans. During the presidential primary, Romney said he had changed his mind and campaigned aggressively on a pro- life agenda.
Romney and McCain showed there was no love lost between them in the primaries, leaving Democrats with a wealth of incriminating video clips that could be used against the ticket.
Tim Pawlenty, 47, is a two-term Minnesota governor who preaches fiscal discipline and limited government. With a proven ability to balance a state budget, Pawlenty brings executive experience to the Republican ticket without the negative primary barbs that would be raised if Romney were McCain's choice.
The youthful governor provides a positive counter to 47-year-old Obama but is untested on a national stage. His lack of foreign policy credentials has some strategists worried that he would struggle in a vice-presidential debate against Biden.
Joe Lieberman, a Democrat-turned-independent who was Al Gore's running mate in 2000, endorsed McCain earlier this year and has since become one of his most vocal supporters. Staunchly in favour of the Iraq war, Lieberman plans to speak at the Republican Party nominating convention next week.
Lieberman's selection would reinforce McCain's image as a maverick who can work with all sides of the political aisle. But Lieberman remains left-leaning on many social and domestic issues, which could prompt a rebellion among a conservative base that is already skeptical of McCain himself.
Other McCain running mate possibilities include Tom Ridge, a former governor of the battleground state of Pennsylvania and the nation's first ever homeland security secretary, a cabinet position created after the September 11, 2001 attacks. Ridge may be untenable to conservatives due to his support of abortion rights.
Bobby Jindal, 37, is a rising star in the party who was elected Louisiana's governor in 2007. Jindal is the first-ever state governor of Indian descent and would provide a youthful counterpunch to Obama. But his relative inexperience would blunt the party's key attack line that Obama is not ready to lead.
Mike Huckabee, a former Arkansas governor and Baptist minister, is the darling of the social conservative movement, but showed little appeal beyond that demographic in his own presidential run this year.