Romney declined Monday to say if Rubio was on his list of vice presidential candidates. He said his campaign is still setting up the infrastructure that's required to scrutinize potential nominees, including hiring legal and accounting staff.
Romney has put longtime adviser Beth Myers in charge of the search process.
"Beth Myers has begun to put together a number of the names and criteria and so forth that would be associated with that process, but we really haven't had a discussion yet of putting together a list or evaluating various candidates," Romney said. "That's a process. We're looking at various people, resources to help with that process."
The former Massachusetts governor also refused to say whether Rubio is experienced enough to serve as his No. 2. Romney often criticizes Obama, who was a first-term senator when he was elected president, as a "nice guy" who is "in over his head," implying that the Democratic incumbent didn't have the experience he needed for the job.
"I don't think I have any comments on qualifications for individuals to serve in various positions in government at this stage. That is something that we're going to be considering down the road," Romney said.
Rubio said he was no longer commenting on the process. He has said he doesn't want the running-mate slot, and some Republicans have urged him to consider running for the top slot in 2016.
Romney, meanwhile, has campaigned with a growing list of possible running mates, starting with New Jersey Gov. Chris Christie, who backed Romney as soon as he definitively decided not to run. Romney campaigned extensively with South Carolina Gov. Nikki Haley before her state's primary in January.
He's also shared the stage with South Dakota Sen. John Thune, Virginia Gov. Bob McDonnell, Wisconsin Rep. Paul Ryan, former Minnesota Gov. Tim Pawlenty, New Hampshire Sen. Kelly Ayotte, and Ohio Sen. Rob Portman. Portman and Ayotte have recently done individual campaign stops for Romney.
The meetings give Romney and his aides a chance to evaluate potential contenders and work with their staffs. In some cases, it's quickly become clear that the operations don't mesh well. In other cases, the rapport between politicians is obvious, as it was with Ryan, who joined Romney before the vote in Wisconsin on April 3.
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