Florida senator heads field after week where he joined Romney on the campaign trail and made major Washington speech
Florida senator Marco Rubio is consolidating his position as the leading candidate in the race to become Mitt Romney's running mate, having set out his foreign policy credentials in a major speech in Washington and promoting a bipartisan bill on immigration aimed at wooing crucial Latino voters.
Rubio, a Tea Party favourite, has begun the process of reinventing himself, possibly with a view to appealing to independents, the voters who will decide the White House election.
The Romney campaign said the process of vetting potential running mates is only just getting under way. Two weeks ago, Romney appointed a former adviser, Beth Myers, to vet the potential candidates, and his staff say he has not yet discussed names with her.
Romney does not have to make a decision until the summer, in the run-up to the party convention in Tampa, Florida, in August.
But Rubio jumped up a few places in the speculation stakes this week when Romney chose him to join him on the campaign trail. Rubio has also shifted from outright denial of interest in being the vice-president to saying he is no longer going to discuss the issue.
Larry Sabato, politics professor at the University of Virginia, said: "He is on everyone's shorlist. Whether he is on Romney's private list, I don't know. I assume he is.
"He would help Romney with Hispanics. He is youthful. He is a favourite of the Tea Party, which Romney is not. He would balance the ticket. On the downside, he has only been in the Senate a year and a half."
Among Rubio's advantages is that he is from a key swing state that went for Barack Obama in 2008 but is a toss-up this time round.
Former Florida governor Jeb Bush is the only other Republican who could help shift the state towards Romney but Politico's Jonathan Martin, in an article Friday, insisted he really does not want it. Bush told a Bloomberg reporter in an email he was not interested. "I am not going to be the veep nominee. Lay that to rest," he wrote.
The vice-presidential slot is a major prize because, win or lose, it sets up the candidate for a tilt at the presidency in 2016 or later.
It is a crowded field. Apart from Rubio, others on the list of potential running mates include Ohio senator Rob Portman, Virginia govenor Bob McDonnell, congressman Paul Ryan, New Jersey governor Chris Christie, Louisiana governor Bobby Jindal, Indiana governor Mitch Daniels, New Mexico governor Susana Martinez and former secretary of state Condoleezza Rice.
Some like McDonnell are openly lobbying for the job. Others are playing it down, professing no interest.
As well as being behind Obama with Latino voters, Romney is also struggling to win over women voters. Potential female candidates include, in additon to Martinez and Rice, South Carolina governor Nikki Haley, New Hampshire senator Kelly Ayotte, and Oklahoma governor Mary Fallin.
One of the strengths of a Rubio candidacy would be his position on immigration reform, which could help undo some of the damage done to Republican party by the anti-immigrant rhetoric from many of the candidates during the primaries and caucuses.
Rubio is proposing that children who were brought to the US by parents who were illegal immigrants should be allowed to stay provided they have a college education or serve in the military. It does not go as far as Democratic propsoals that would offer a route to citizenship.
Rubio spent part of the week in Congress lobbying among both Republicans and Democrats for this proposed reform, even though the Republican House speaker, John Boehner, expressed doubts about whether it could pass.
At a press conference, Boehner said: "The problem with this issue is that we're operating in a very hostile political environment. To deal with a very difficult issue like this, I think it would be difficult at best."
Rubio won favourable media coverage this week for a major speech at the Brookings Institution in Washington, setting out his foreign policy position, some of which challenged Republican orthodoxy, particularly the present retreat by the party towards isolationism.
Rubio is set to become centre stage again in the summer when two books about him are published on 19 June, one an autobiography and the other a potentially critical biography.
Tom Mann, a Brookings Institution political specialist and co-author of a book about gridlock in Washington being published on Tuesday, said: "Rubio is 40 and looks younger. I assume the speech was to establish a little gravitas."
The first rule for a vice-presidential candidate, according to Mann, is to do no harm. "It is easier to be hurt by a vice-presidential candidate than helped. We have a few cases of a postive difference being made but the danger is they can get in the way of a candidate. Sarah Palin would be a good case."
A bad choice is not necessarily devastating, citing the example of George Bush Sr's 1988 running mate Dan Quayle, "who looked like a deer frozen in headlights on a dark night – but in the end it was not consequential." Bush won the election from Michael Dukakis.
Mann thinks journalists and pundits get it wrong in focusing on the impact of a running mate, and should be looking instead at the qualities they would bring to government, given that increasingly vice-presidents are given jobs to do – and also the possibility that they might even have to take over the top job.
Mindful of the searing experience of the 2008 campaign when John McCain failed properly to vet Palin, a last-minute choice of a relative unknown seems unlikely. Myers is more likely to resort to the usual, time-consuming vetting process, setting researchers to work on the potential candidates, drawing up dossiers on them, interviewing them in private, winkling out all the potential damaging detail from a candidates' past that could explode during an election campaign.
Sabato said a danger in the vetting process is that those conducting it have a temptation to want to come up with the names of someone people will not have thought of. "That is how you come up with Sarah Palin or Dan Quayle or Geraldine Ferraro, who should not have been picked," Sabato said. "Our history is littered with mistakes."
A Republican strategist, Ron Bonjean, noted that choice of candidate is a difficult balancing act. "Clearly there are risks to having someone who is more dynamic or who is more of a firecracker than yourself," Bonjean told Reuters.
"The benefit of having a someone who is much more dynamic than you is that it creates excitement around your candidacy. The downside is if this person goes off message and over-reaches, it can have a negative impact on the campaign."
Given the vitriolic nature of the primary and caucus campaign and the exposure of their quirks and vulnerabilities, none of Romney's former rivals in the nomination process – Rick Santorum, Newt Gingrich, Ron Paul, Michele Bachmann, Jon Huntsman , Herman Cain, Rick Perry or Tim Pawlenty – appear likely to be in the running. Pawlenty, former governor of Minnesota, is the mosy sober of that field, but he fought a dull campaign.