Democrats have started to wage a political assault against Sen. Marco Rubio (R-Fla.), and the intensity of their attacks will intensify in the coming weeks.
Senior officials in the Democratic Party anticipate that Mitt Romney will win the Republican presidential nomination and then tap Rubio to be his running mate.
The former Massachusetts governor has a long way to go before he secures the GOP nod, but that hasn't stopped Democrats from launching early salvos at the freshman senator.
Senate Majority Leader Harry Reid (Nev.), who has not been shy in lambasting GOP White House hopefuls in prior election years, has questioned whether Rubio really stands with the Hispanic voters with whom he is so popular on the issues most important to them.
Meanwhile, Democratic National Committee Chairwoman Debbie Wasserman Schultz (Fla.) tried to drive a wedge between Rubio, who is Cuban-American, and Hispanic voters.
Democratic operatives have turned their attention in recent months to Rubio's personal finances and his family background, going on digging missions that are usually reserved for presidential candidates.
And campaign fundraising reports show that Rubio spent more than $40,000 in the last six months of 2011 to get himself researched by a public affairs firm — presumably to prepare for the wave of Democratic attacks against him.
Democrats say Rubio's record did not get adequate scrutiny in 2010 when he won a three-way Senate race against former Florida Gov. Charlie Crist, who ran as an independent, and former Rep. Kendrick Meek (D-Fla.).
"I think Marco Rubio benefited in 2010 from a three-way race. There are some things about his record that probably did not get the scrutiny they deserve. I think the higher that he rises, the more people will start to look at some of those issues. He will have to be held accountable," said Rodell Mollineau, president of American Bridge 21st Century, a Democratic super-PAC that specializes in opposition research.
Rubio's advisers are working to inoculate their boss from the deluge of opposition research and attacks that inundated former Alaska Gov. Sarah Palin after she was named Sen. John McCain's (R-Ariz.) running mate in 2008.
"Marco's campaign in 2010 couldn't afford adequate research so we're doing it now, since we know press are digging into things like his family history and his student loans and liberal super-PACs like American Bridge are doing oppo [research] dumps," said Alex Conant, Rubio's spokesman.
"It's clear the Obama White House and other liberals are somewhat obsessed with trying to knock him down, but the senator is focused on representing Florida in the U.S. Senate and fighting for conservative ideas," he added.
Rubio, who has refrained from endorsing in the GOP presidential primary, has said he is not interested in running with Romney on the GOP ticket.
But Democratic officials are skeptical of that claim.
"No one publicly campaigns to become vice president. We shall see what he says should the Republican nominee come knocking at his door," said Mollineau.
Rubio, 40, would be an appealing running mate because he represents Florida, a crucial presidential battleground state. Rubio's skills as an orator and his Hispanic heritage clearly have Democrats worried.
Hispanic voters represent the fastest-growing major bloc of the electorate and could make the difference in swing states such as Colorado, New Mexico and Nevada.
The first prong of the Democratic strategy against Rubio is to divide him from most Hispanic voters, who favor policies that Rubio has opposed such as the DREAM Act, which would grant legal residency to illegal immigrants who came to the country at a young age and meet certain conditions.
Wasserman Schultz has accused Rubio of being out of step with the greater Hispanic community. In January, she said a Romney-Rubio ticket would be "extreme."
"If there's a ticket like that, it would be the most extreme ticket in history when it comes to immigration," she told CNN.
Reid has questioned whether Rubio stands with Hispanics after the Florida senator voted against procedural motions on President Obama's nominee for ambassador to El Salvador. Rubio later said he supported the confirmation of Mari Carmen Aponte, who is Puerto Rican and served on the board of the National Council of La Raza. Regardless, Rubio's stance handed Democrats a talking point.
Democrats have also highlighted Rubio's opposition to the DREAM Act.
"Marco Rubio does not represent what the Hispanic community is. He really doesn't represent a lot of Puerto Ricans, Dominican Americans and Mexican Americans," said Cesar Vargas, a lobbyist representing people who support the DREAM Act.
Vargas said the legislation is popular with many Hispanics of different backgrounds.
"He prefers to choose his party over his people," said Vargas, who has volunteered for Democratic candidates in the past.
In the coming weeks and months, Democrats will home in on Rubio's support for an Arizona law requiring non-citizens to carry immigration papers at all times. Four out of five Hispanics oppose that law, according to a recent survey.
At first, Rubio spoke out against the measure, but then said he would vote for it after it was changed to limit when police are able ask for documentation.
Immigration reform proposals, even scaled-down proposals such as the DREAM Act, have no chance of passing Congress this year. Yet Democrats are expected to seek votes on immigration reform later this year, as they did before the 2010 election.
Reid participated in a conference call with reporters Monday to criticize Romney's stance on immigration.
"Republicans love to talk about how high the fences should be, they talk about electrifying the fences, they've talked about notions like self-deportation, they've talked about vetoing bills, something as sensitive and as pure as the DREAM Act," Reid said.
The majority leader was making reference to Romney, who used the term self-deportation during a debate and said he would veto the DREAM Act if elected president.
The second prong of the Democratic strategy is to raise attention over Rubio's personal finances and background.
Democratic strategists have circulated press reports that Rubio charged more than $100,000 worth of travel and meals on a credit card billed to the Republican Party of Florida, which led to an IRS investigation, according to the St. Petersburg Times.
Rubio has strongly defended his use of the credit card and denied that the IRS launched a probe.
Democratic strategists have also drawn attention to an article last fall in The Washington Post that reported Rubio had mischaracterized his family background by claiming that his family fled Cuba during the Castro revolution.
Rubio later acknowledged his family left the island before Fidel Castro seized power, and attributed the misimpression to imprecise storytelling within his family.
He called the suggestion that his family's story was embellished for political gain "outrageous." Rubio added that the "essential facts of my family's story are completely accurate."