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Even before the Republicans chose a presidential nominee it was widely assumed that Sen. Marco Rubio, R-Fla., would be at the top of anybody's list of vice presidential candidates. The reasons are obvious: Not only is he young, charismatic and wildly popular with conservatives, but he could also help Republicans win a key state (Florida) and make inroads with Hispanics.

But knowledgeable Republican sources tell me that Rubio is not being vetted by Mitt Romney's vice presidential search team. He has not been asked to complete any questionnaires or been asked to turn over any financial documents typically required of potential vice presidential candidates.

Although it is possible that Rubio may yet be asked to go through the vetting process, it has been nearly two months since Romney named his long-time aide Beth Myers to run his vice presidential search. The fact that Rubio has not been asked to turn over any documents by now is a strong indication that he is not on Romney's short list of potential running mates.

Officially the Romney campaign has no comment. And Rubio has refused to make any comment when it comes to vice presidential questions. As Rubio spokesman Alex Conant told me, "We have no comment on the vice presidential search process."

The news will be disappointing to prominent conservatives - including Sen. Jim DeMint and former Florida Gov. Jeb Bush - who have been openly encouraging Romney to pick Rubio.

"Marco would bring incredible energy," Bush told ABC News on June 1. "He's the most articulate spokesman for conservative principles in American today, and he is my friend, so I am a little biased. I think he would be extraordinary."

Get more pure politics at ABC News.com/Politics and a lighter take on the news at OTUSNews.com

Whether or not he is on Romney's short list, Rubio has already been an asset to the Romney campaign. In virtually every interview he has done recently, Rubio has praised Romney and defended him on issues ranging from taxes to immigration. And on Tuesday night, Rubio plans to take part in a fundraiser for Restore Our Future, the Super PAC supporting Romney.

For his part, Romney frequently praises Rubio on the stump, touting Rubio's story as the son of Cuban immigrants as an example of the American dream.

"[Rubio] said something that will stay with me a long time," Romney said at a recent rally in Council Bluffs, Iowa. "He said when I was a boy living poor in this country with my family, we saw some other homes, great big homes and fancy cars. He said, 'I never heard my parents say why can't we have what they have. Instead my parents said aren't we lucky to live in a country where with education and hard work, there's a shot we have of earning that ourselves.' That's the nature of America. We're the land of opportunity."

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