Political vulnerabilities in Sen. Rubio’s past?

The 40-year-old Florida lawmaker has close ties to a colleague accused of questionable financial dealings. He once was enmeshed in a controversy over the use of the state party's credit card for his personal expenses. Since emerging on the national political scene, he has faced increased personal scrutiny. There are conflicting details about his parents' immigration from Cuba and his recently disclosed ties to the Mormon faith.

The effect of those issues on his political fortunes is the subject of debate in Republican circles in Washington, Florida and elsewhere as the Cuban-American senator with solid conservative credentials works to raise his profile beyond his home state and possibly position himself for a national role.

“Marco Rubio is a huge star in the Republican Party in much the same way that Barack Obama was in the Democratic Party between his convention speech in 2004 and his candidacy for the president,'' said Steve Schmidt, a top adviser to GOP Sen. John McCain's 2008 presidential campaign. “There are a lot of pluses when you look at Marco Rubio as a potential vice presidential candidate, but there are also unknowns.''

Rubio frequently is mentioned by Republican insiders as an attractive candidate to be Romney's vice presidential pick, partly because the GOP needs to attract Hispanic voters in pivotal states such as Nevada and Florida.

Rubio denies any interest in the No. 2 spot this year, but he's working hard to stay in the national spotlight. He recently gave a major foreign policy address in Washington. He's talking about writing a bill to allow some young illegal immigrants to remain and work in the country without citizenship. Next month, he'll release a memoir.

The country is only just starting to get to know Rubio and his political vulnerabilities, though Florida residents know both well.

Both Rubio's ties with U.S. Rep. David Rivera, a fellow GOP freshman who now is facing a federal probe into tax evasion, and the state party credit card matter surfaced during Rubio's 2010 Senate campaign. While they didn't have much effect, that doesn't mean they would get a pass on the national stage.

“Floridians may be numb to these hits because of the rough-and-tumble nature of politics in the state, when it's looked at by a national audience it may not be as palatable,'' said Abe Dyk, a political strategist who managed the 2010 Senate campaign of Rubio's Democratic challenger.

Rubio and Rivera met in 1992, during the campaign of former Republican Rep. Lincoln Diaz-Balart, a fellow South Florida Cuban-American. The two rose through the ranks in the Statehouse with Rivera oftentimes playing bad cop to the more congenial Rubio.

During the legislative session, they shared a Tallahassee town house, which a bank began foreclosure proceedings on in 2010. Rubio and Rivera made only partial payments on that mortgage for five months in 2010; at that time, he held jobs as a consultant and professor. Rubio has said the missed payments were due to a dispute over the terms of the mortgage.

State officials closed a criminal probe into Rivera's personal financial dealings without filing charges but didn't clear him entirely. They cited Florida's brief statute of limitations and its lax campaign finance laws for not charging him with living off of his campaign funds and failing to disclose his income.

In the last year, Rubio has publicly kept some distance from Rivera and has said that his friend has some issues he must address on the campaign trail. Still, Rubio threw a small Washington fundraiser for Rivera last week. So far, Rubio hasn't faced blowback from his friendship with Rivera.

“It's tough to say how that will play out,'' says Emilio Gonzalez, a consultant who served in the Bush administration and sees Rubio as a potentially formidable presidential candidate in 2016.

If Rubio were to end up on the GOP presidential ticket or mount his own national campaign in the coming years, he all but certainly would face questions about the scandal over the use of state GOP funds when he was the speaker of the Florida House.

The head of the party, Jim Greer, was forced to resign following revelations he and his second-in-command charged $1.5 million on party credit cards, much of it on luxurious hotels, fancy restaurants, chauffeured sedans and lavish entertaining. Greer's trial is set to start July 30, just ahead of the Republican convention, and many Republican observers anticipate he will detail unethical use of party money by other high-ranking GOP officials.

Rubio spent more than $100,000 on the party card between 2006 and 2008, paying off about $16,000 in personal expenses and claiming the rest as official party business. His records from 2005, when he was lobbying to become Florida House speaker, never were released. When asked about using the party card for personal expenses, Rubio has said he sometimes just pulled the wrong card out of his wallet and he has called it a “lesson learned.''

He also has had to answer criticism for how he spent money donated to two political committees he formed – including payments to relatives. He has acknowledged the bookkeeping for at least one of the accounts was sloppy.

Then there's his family's background.

Rubio long claimed his parents fled Fidel Castro's rule. But it was recently disclosed that they arrived several years before Castro took power, although they quickly embraced the Cuban exile community as Castro turned toward communism. Rubio has said the dates he gave were based on his parents' recollections.

There's another part of Rubio's upbringing that long had gone undisclosed, and the revelation is one that could turn off evangelicals who make up the base of the GOP.

Rubio was baptized as Mormon when his family lived for a few years in Las Vegas, thanks to the influence of cousins who belonged to The Church of Jesus Christ of Latter-day Saints. Rubio returned to the Catholic Church as a young teen, and as an adult he has also frequently attended Baptist services.

When it comes to the vice presidency, Rubio's greatest liability may be one only time can resolve.

“I suspect that the Romney campaign is going to pick someone who is viewed as unquestionably qualified for the office,'' said Schmidt, who was intimately involved in McCain's selection of Sarah Palin. “To the extent that (Rubio's) in his first term, he's in the first two years of his term and he's 40 years old probably doesn't help him.''