Who will be on McCain's ticket?

Senator John McCain is expected to be confirmed as the Republican candidate for the US presidency at the party's convention in September.

Before then, he will need to choose a running mate, who will become his vice-president, if the pair win the election.

The BBC News website takes a look at who is in the frame for the job.

CHARLIE CRIST

The popular Florida Governor may well have tipped the balance for Mr McCain when he endorsed him ahead of his state's crucial primary earlier this year.

Born: 24 July 1956 Status: Governor of Florida Advantage: From a battleground state Disadvantage: Liberal on some social issues

He is young enough to complement Mr McCain, and he could help to ensure that the swing state of Florida stays in the Republican column in November.

He believes in low taxes and small government, which could help Mr McCain win votes among fiscal conservatives, but has relatively liberal views on civil unions and stem cell research.

On 3 July, Mr Crist announced his intention to marry for a second time, scotching speculation about his sexual orientation.

Mr McCain has refused to say whether he is considering Mr Crist as a running mate, but has said "there are many ways for him to serve the country".

TOM RIDGE

On paper, Tom Ridge would appear to tick every running-mate box for John McCain.

Born: 26 August 1945 Status: Former Homeland Security Secretary and Governor of Pennsylvania Advantage: Security credentials and swing state connections Disadvantage: Pro-choice views unpopular with base

As a former Homeland Security Secretary, he has strong anti-terrorism credentials.

And as a former governor of Pennsylvania, he would give Mr McCain a shot at winning a key swing state.

Perhaps most importantly, he and Mr McCain share a close personal bond.

But Mr Ridge's pro-choice views have made him unpopular with the Republican base - which already has its doubts about Mr McCain himself.

So the Arizona senator is likely to be obliged by his party activists to pick a pro-life running-mate - which would rule Mr Ridge out of the running.

MARK SANFORD

The South Carolina governor was a loyal McCain supporter when the Arizona senator ran unsuccessfully for the Republican nomination in 2000.

Born: 28 May 1960 Status: Governor of South Carolina Advantage: Popular with conservatives Disadvantage: Late to endorse Mr McCain

But this year he only endorsed Mr McCain after he had secured the nomination, which considerably reduces his chances of being named as running mate.

Like Mr McCain he has voted against spending increases, even when doing so might win votes, which makes him popular with conservatives.

He has said there are two ways to improve standards of living - through brain power and intelligence. By coincidence, these are two qualities Mr McCain says he would like to see in a vice-president.

He spent three terms in Congress before defeating an incumbent Democrat for the governorship in 2002. However, in presidential elections South Carolina is a safe Republican state.

TIM PAWLENTY

Minnesota could be a key election battleground, and the state's popular governor, Tim Pawlenty, is seen as one of the hot favourites for Mr McCain's running-mate.

Born: 27 November 1960 Status: Governor of Minnesota Advantage: Solid conservative credentials Disadvantage: May not be able to deliver Minnesota

Mr Pawlenty endorsed the Arizona senator back in 2006 and is now national co-chairman of his campaign.

Like governors Crist, Sanford and Barbour, Mr Pawlenty is more conservative than Mr McCain, and at only 47, he also has youth on his side.

He is in his second term as governor, having taken over from Reform Party member and former professional wrestler Jesse Ventura. He is also chairman of the National Governors Association.

In 2004, Minnesota only narrowly voted for Democrat John Kerry, and it features on most lists of swing states in 2008. However, some analysts predict that the state could vote Democrat again, even if Mr McCain does choose Mr Pawlenty as his running mate.

The Republican National Convention will be held in Minnesota in September.

CONDOLEEZZA RICE

Born: 14 November 1954 Status: US Secretary of State Advantage: High profile Disadvantage: Says she doesn't want the job

Mr McCain could tap into the excitement some voters feel about the Democratic Party's first black presidential candidate by choosing as his running-mate a young, African-American woman.

US Secretary of State Condoleezza Rice also has masses of experience, both in her present job, and in her previous job as national security adviser.

She is also popular within the party, and a formidable debater.

Liberal weekly The Nation suggests "she may be enough to elect the venerable hero/naval aviator".

However, she has explicitly said that she does not want to be anyone's running mate and intends to return to Stanford University, where she is a professor of political science.

KAY BAILEY HUTCHISON

The Texas senator, often known as KBH, is one of very few women mentioned as a potential running mate for Mr McCain.

Born: 22 July 1943 Status: Texas Senator Advantage: A rare female contender Disadvantage: Doesn't want to be vice-president

She became the first woman senator for Texas in 1993 and was re-elected in 2006 with 62% of the vote. As chair of the Republican Policy Committee in the Senate, she is the fourth-highest-ranking Republican senator.

She has a mostly conservative voting record, but is opposed to outlawing abortion and is in favour of embryonic stem cell research.

She also has said explicitly: "I don't want to be vice president". Her preferred career move would be to run for the Texas governorship in 2010.

Texas will vote Republican whether or not she is on the ticket, so she would bring Mr McCain no extra electoral college votes.

GEN DAVID PETRAEUS

Born: 7 November 1952 Status: Commanding General, Multi-National Force - Iraq (from September, head of US Central Command in Middle East) Advantage: Strong national security credentials Disadvantage: Little political experience

If Mr McCain wanted to bolster his national security credentials and emphasise his support for action in Iraq, then he might pick someone like Gen David Petraeus.

Gen Petraeus has been in charge of US forces in Iraq since the troop "surge" in 2007.

Little about his views on non-military matters is known, however, so Mr McCain may shy away from appointing him to such a high-profile position.

And whether Gen Petraeus would even accept an offer from Mr McCain is not clear.

JOE LIEBERMAN

The Connecticut senator might be another left-field choice. He was Democratic presidential candidate Al Gore's running-mate in 2000, but later became an independent Democrat.

Born: 24 February 1942 Status: Connecticut Senator Advantage: Early supporter of Mr McCain Disadvantage: Liberal views

In December, Mr Lieberman endorsed Mr McCain ahead of all of the Democratic presidential candidates.

Although he is respected by Republicans for his conspicuous support of the Iraq war, his views on certain social and economic issues would probably be too liberal for many party activists to stomach.

Choosing him would not exactly endear Mr McCain to the conservative core of the Republican party and it is questionable whether he would appeal to enough wavering Democrats to warrant a place on the ticket.

MIKE HUCKABEE

Despite media speculation, Mr McCain is unlikely to add his primary opponent Mr Huckabee to his ticket.

Born: 24 August 1955 Status: Former Arkansas Governor Advantage: Campaign experience Disadvantage: Liberal on spending issues

Although Mr Huckabee could broaden Mr McCain's appeal among evangelical voters, he would be as unpopular as Mr McCain himself is with influential conservative commentators, who are critical of Mr Huckabee's populist stance on government spending.

Mr Huckabee has the advantage of having been tested in recent elections - the Republican primaries - and was the only serious contender left in the race until Mr McCain became the nominee.

Both men campaigned together in Arkansas in late April and seemed at ease in each other's company. But would Mr McCain be happy with the thought of leaving America with President Huckabee, if anything should happen to him?

MITT ROMNEY

Mr McCain's other main primary rival would be popular with fiscal and social conservatives - sections of the core Republican support base that Mr McCain is keen to court.

Born: 12 March 1947 Status: Former governor of Massachusetts Advantage: Popular with conservatives Disadvantage: Little personal chemistry with Mr McCain

The former presidential candidate is clearly keen on being picked, and has been actively making the case for Mr McCain across the media.

He also has executive experience, as governor of Massachusetts, and a strong economic background - unlike Mr McCain, who has said he does not know as much about the economy as he should.

He also has a high profile and a strong support base and could easily mobilise supporters across the country.

If Mr McCain believes campaign experience is important, then Mr Romney has won primaries in several potential battleground states like Colorado, Michigan and Minnesota which could prove useful in November.

Reports suggest the two men have become friends since the primary campaign - but at the time they clearly did not get along.

ROB PORTMAN

Rob Portman was, until June 2007, President George W Bush's director of the Office of Management and Budget and previously his trade representative.

Born: 19 December 1955 Status: Lawyer Advantage: Economy and trade experience Disadvantage: Little campaign experience

He has been touted as a possible running mate for Mr McCain by Mr Bush's close adviser Karl Rove, because of his economic and trade experience.

Mr Portman was previously a congressman from Ohio, which, as a battleground state, works in his favour.

Conservative pundit Robert Novak summarised Portman's pluses this way: "(His) background is legislative (House Republican leadership), executive (George W Bush's Cabinet), diplomatic (US trade representative) and economic (Office of Management and Budget director). He comes from a swing state (Ohio), is young enough (52) to contrast McCain and conservative enough (89% lifetime rating by the American Conservative Union)."

He is rumoured to be interested in running for the position of governor of Ohio in 2010.

JOHN THUNE

Born: 7 January 1961 Status: South Dakota Senator Advantage: Perceived as a winner Disadvantage: Relatively inexperienced

The South Dakota senator entered the Senate in 2004 with a reputation as a giant-killer, after he unseated Senate Minority Leader Tom Daschle in the most expensive election of the year.

He has voted against the White House on occasion, but this would not alarm Mr McCain, and could be an advantage in a year when the incumbent Republican president is deeply unpopular.

He is a junior senator but also familiar with Washington, having served in the House of Representatives for three terms.

He is also young - born in 1961 - and good looking, which never hurts.

BOBBY JINDAL

Born: 10 June, 1971 Status: Louisiana governor Advantage: Youthful, with a multi-ethnic appeal Disadvantage: Possibly too young and inexperienced

Bobby Jindal's 2007 victory in the Louisiana governor's race set him apart as one of the Republican Party's rising stars.

The party has been keen to push Mr Jindal - an Indian-American - forward as an example of its growing diversity.

Mr Jindal - who is a devout Catholic and who ran his gubernatorial campaign on a platform of cracking down on government waste and corruption - is a darling of the party's conservatives.

He has been talked about as a potential vice-presidential pick, but many observers believe he lacks the necessary experience and that - at just 37 - he is just too young for the job.