The next president's Robin

Who will the presidential candidates in the race for the White House choose to be their running mate

In a particularly memorable statement that rather aptly summarized his central role in the first Bush presidency, Vice President Dan Quayle said he yearned to be "Robin to Bush's Batman".

While the seemingly never-ending primary season we are starting to see the conversation moving on to actual presidential campaigns, with one of the biggest questions of course being: who are the candidates likely to be for the number two slot?

The key thing with vice presidential candidates according to Dr Paul Rundquist, a visiting professor at the London School of Economics with 30 years experience in Capitol Hill, is that "you try to figure out where you are weakest as a candidate, and try to fill those gaps".

In other words, you use your vice presidential candidate to reach out to a constituency you worry might otherwise go to the other side - usually in the form of a someone from a keenly contested state, or someone whose personality touches a societal strata which might hesitate to vote for you. So if you are perceived as a godless tax raiser who is distrusted by his own base (step forward Senator McCain ), then you aim for a Veep candidate who is has gone on record as wanting to abolish the Internal Revenue Service (IRS) and has taken holy orders (step forward Governor Huckabee).

This seems a natural pairing for Dr Rundquist, who sees Governor Huckabee's popular conservatism, state governmental experience (as Governor of Arkansas), and "proven ability to win votes in the Southern states" as factors that might appeal to Republican strategists who see all of these issues as possible holes for Maverick McCain.

However, for Alexandros Petersen, Section Director North America at the Henry Jackson Society and a longstanding McCainiac, Huckabee overplayed his hand, "he seemed to be angling for the VP spot under McCain, but he seems to have scuttled his chances by staying in the race too long".

He instead sees McCain taking on a number two along the lines of Governor Tim Pawlenty of Minnesota, "a young, exceedingly-popular governor with a catchy nick-name: 'T-Paw'". Pawlenty has been a staunch McCainiac from the beginning and his strong stance on immigration might balance some of the questions over Mack's perceived weakness on this topic, and finally, Minnesota is a key state for the Republicans come the election.

There is, however, one candidate on the Republican side that both Rundquist and Petersen, and the U.S. punditocracy all agree on, and that is the fabled Governor Charlie Crist of Florida. Already responsible for securing the state for Senator McCain in the primaries (and consequently doing the world a great service by putting the much needed nails in the coffin of the terrifying Giuliani campaign), Crist is a hugely popular governor in a state that has repeatedly proved to be central to U.S. campaigns (anyone remember the 2000 hanging chads?).

The problem with Crist, however, is best summarized by Dr Rundquist's point about the awkward nature of Senator McCain choosing another "old white man with white hair to help him run for president." If the Mack is facing off against either the first female or first African American to run for the highest office in the land, it will be an awful hard sell to present himself as something fresh and new if he is running with another silvered haired Southern gent.

This finally turns us to the Democratic race, which is a hard one to call in this field since a conclusion is by no means on the horizon. The fact that none of the heavy hitter candidates in the race who dropped out earlier (John Edwards or Governor Bill Richardson) have chosen to give their endorsement to each candidate is telling - both would bring substantial heft to either a Clinton or Obama ticket, and it is a time honoured tradition to bring on a close competitor in the primaries as your number two.

But the real question on everyone's mind is whether Obama and Clinton could team up. Traditional wisdom would dictate that while he could be seen to do it for her, she could never do it for him (the humiliation on her behalf, while he is still a young chap and could wait out eight years to season in the public eye and then sweep in as the incumbent - a sort of Gordon to her Tony). Paul Rundquist, however, sees it quite differently: "Obama does not see himself as a career politician - he isn't going to serve four terms in the Senate. Clinton on the other hand is a career civil servant."

For Hilary, there are more career options left in politics. "If she loses the presidential election, she could leverage her insider position to become the party leader in the Senate. If she loses the primaries and shows her loyalty by taking the vice presidential position, it would work for her either way."

This is certainly what some inside the party are already hoping for; Democratic National Committee chair Howard Dean has already hinted that "we are going to have to get the candidates together and make some kind of an arrangement," and others have salivated at the opportunity of a Clinton-Obama "dream ticket."

The problem is that both candidates can see victory within reach, and consequently neither is willing to cede to the other in such an overt way - Senator Clinton's offer that she would take Obama on as her number two was little more than a bid to paint herself into the superior position.

Ultimately, whoever is chosen will be stepping into the substantial shade thrown by the Cheney vice presidentship, that has been characterised as more of a co-presidency. Back in the day, Vice President Truman was only in the job for three months when Roosevelt died. This time has passed and now the challenge is not to get stuck with a Dan Quayle (President Bush I's deputy who once boldly announced that "[it's] time for the human race to enter the solar system"), or a crook like Spiro Agnew who President Nixon brought on to assuage his conservative base and was eventually forced to quit after pleading guilty to charges of bribery and tax evasion.

Rest assured that we are not going to see any resolution to this question any time soon. Senator McCain will keep his powder dry until he knows what he is facing off against, and, for the Democrats, they need to decide who is actually going to run against him before they start choosing who will support whoever is running against him.

For us in Europe, this entire debate matters little - except for the fact that there is a strong possibility that whoever ends up with the Veep job will be the one who spends him time travelling around the world assuring us nervous European nellies that they are actually doing something about climate change.