Image credit: Alan Diaz/AP Photo

From his first days on the political scene, Sen. Marco Rubio has never strayed far from his close friend, Rep. David Rivera. The men first met while volunteering for then Florida State Senator Lincoln Diaz-Balart's first congressional campaign in 1992.  A few years later, Rivera hired Rubio out of law school in Miami to work on Bob Dole's doomed presidential bid.

By 2002, they were colleagues in the Florida state house and when Rubio was elected speaker in 2006, Rivera took up as his top lieutenant. They rode into Washington together on the crest of a powerful GOP midterm wave in 2010, Rubio as a senator, Rivera as the new house representative from Florida's 25 th district.

Today, Rubio is one of the Republican's party's most buzzed-about young stars and an early favorite to run alongside presumptive Republican presidential nominee Mitt Romney in the coming general election. Despite repeated statements that he "won't be the vice president," operatives in both parties told ABC News they believe Rubio is seeking the bid.

"He wants it," one Democratic strategist said. "He can say what he wants, but he's doing all the things that people who want to be the running mate do. He's going to South Carolina [to speak before state party bigwigs at their annual Silver Elephant dinner] and working on some Republican version of the Dream Act."

What Rubio has not done - and recently told POLITICO he never will - is break his ties to David Rivera.

Featured prominently in the non-partisan "Citizens for Responsibility and Ethics in Washington" 2011 "Most Corrupt" list, Rivera has been "under investigation by at least five different law enforcement agencies for a range of violations," including payments he allegedly received in connection with the successful campaign (led, at times, by his mother's consulting firm) to legalize slot machines at horse and dog-racing tracks.

(On Wednesday night, The Miami Herald reported that Rivera would not be charged by state prosecutors for actions detailed in a scathing report by the Florida Department of Law Enforcement because the statute of limitations had expired on the alleged crimes. The same Herald story maintains that the IRS and FBI are still investigating his role in a $510,000 payment made by dog track owners to his mother and godmother's firm.)

The alleged dog track shenanigans cap off a decade of sometimes odd brushes with the law. On Sept. 6, 2002, the Florida Highway Patrol recorded an incident in which a car driven by Rivera ran a truck carrying flyers authored by a political opponent off the road, forcing it to the shoulder. The delay kept the potentially damaging mailers on board from arriving at the post office before a 6 p.m. deadline.

Rivera said in a statement shortly after the incident that the truck was carrying his mailers, too, and that he was only trying to retrieve his own materials.

Earlier this year, House Majority Leader Eric Cantor expressed "concern" about the probes and at least one GOP strategist, speaking to ABC News, referred to Rivera as one of the "possible skeletons in [Rubio's] closet."

Asked if he was concerned that the allegations, from the 2002 highway incident to the dog track controversy and the revelation that he had not, despite reporting it as a source of income, ever worked for USAID, could hurt his friend Rubio's standing in the party, Rivera told ABC News, simply, "No."

When pressed for specific details about the timeline of events surrounding a threatened foreclosure on - and eventual decision to sell - a home he and Rubio bought together in Tallahassee during their time in the statehouse, Rivera said, "You'll have to ask Marco."

Faced with that, a spokesman for Rubio wrote: "The issue over the home mortgage payments has been really well documented. There was confusion over the payments, and Sen. Rubio paid the bank as soon as he became aware of the issue."

The reality is a bit more complicated. Rivera said the bank "was overcharging us," so he and Rubio decided to withhold payment until the dispute was settled. But it was only after Deutsche Bank filed suit and threatened to foreclose that Rubio delivered a check to the mortgage company's lawyers.

Later on they tried and failed to sell the home. "The real estate market is still really struggling there," Rivera said. The property is now being rented.

Even with allegations and investigations swirling, Rubio has remained steadfast by his friend's side. He will hold a fundraiser for Rivera in Washington, D.C., later next month and, according to Rivera, Rubio speaks to him regularly about matters both personal and political.

"I don't think there's another vice presidential candidate that could energize the ticket the way Marco could," Rivera said over the phone Monday night. "Both in substance and style, he has the ability to communicate an optimistic and conservative message.

"But he's told me in private exactly what he's said in public, that he's not going to be picked. He has told me he's not going to be picked [as Romney's running mate.]"

One GOP strategist with strong ties to Florida state politics, Tim Baker, said he "takes Sen. Rubio at his word that wants to remain a great senator from Florida."

And that may well be the case, but after years operating at the center of South Florida's politically powerful Cuban-American community, Rubio must maneuver carefully. Breaking with Rivera could solve one problem, but create another, more damaging set of circumstances.

If Rubio's appeal as a running mate is primarily rooted in his perceived ability to rally the Hispanic vote, which broke strongly for President Obama and the Democrats in 2008, it is critical that he has the full support of his constituency back home. Should Miami turn its back on him, his very reason for cutting ties with Rivera - ending their very real friendship - would be mooted and his Florida-based political career placed in unique peril.