Story highlights Christie and his family starred in ads for New Jersey tourism after Sandy

New Jersey Democratic Rep. Pallone said he was concerned about bidding process

Christie fired two aides last week over the George Washington Bridge scandal

Christie's office says it worked with the Obama administration on marketing plan

Just days after dismissing two top advisers for their roles in the George Washington Bridge scandal, New Jersey Gov. Chris Christie faced questions over the use of Superstorm Sandy relief funds.

CNN has learned that federal officials are investigating whether Christie improperly used some of that money to produce tourism ads that starred him and his family.

The news couldn't come at a worse time for the embattled Republican, who is facing two probes in New Jersey of whether his staff orchestrated traffic gridlock near the country's busiest bridge to punish a Democratic mayor who refused to endorse his re-election.

If the Sandy inquiry by a watchdog finds any wrongdoing, it could prove even more damaging to Christie's national ambitions. He's considered a possible presidential candidate in 2016.

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Photos: Political dirty tricks Photos: Political dirty tricks Political dirty tricks – Aides and appointees of New Jersey Gov. Chris Christie have been accused of closing lanes on the George Washington Bridge to punish Fort Lee Mayor Mark Sokolich, pictured, for not endorsing Christie for re-election. If true, this wouldn't be the first time an American politician was targeted with dirty tricks -- the practice goes back as far as running for office. Click through to see other examples of less-than-ethical campaign tactics. Hide Caption 1 of 7 Photos: Political dirty tricks Political dirty tricks – Prostitution allegations: Sen. Robert Menendez of New York denied that he paid a woman for sex, saying allegations that he did were part of a smear campaign. "Any allegations of engaging with prostitutes are manufactured by a politically motivated right-wing blog and are false," Menendez's office said in a statement. The alleged prostitute later filed a notarized statement saying she had never even met Menendez. Hide Caption 2 of 7 Photos: Political dirty tricks Political dirty tricks – Fake letters: Sen. Edmund Muskie of Maine, running for president, was expected to do well in the 1972 Democratic primary in neighboring New Hampshire. But the Manchester Union-Leader published a letter alleging that Muskie condoned the use of the term "Canuck," a derogatory term used against French-Canadians. Muskie denied the charge but still suffered at the polls in the early primary, which doomed his chances. The Washington Post later reported that the letter was a hoax and was probably written by Ken Clawson, deputy White House communications director in the Nixon administration. Hide Caption 3 of 7 Photos: Political dirty tricks Political dirty tricks – Watergate: The break-in at the Watergate office complex was just the tip of the iceberg in regards to what was going on within President Nixon's re-election campaign in 1972. The Nixon machine was hell-bent on destroying its opponents, and Donald Segretti, pictured, was one of the primary dirty tricksters. The Nixon operative printed fliers that attacked Muskie on his stance against Israel, and he placed them outside synagogues. He also pitted Democrats against one another in a tactic he called "rat-f---ing," like the letter addressed from Citizens for Muskie that accused Democratic primary rival Sen. Henry Jackson of being a homosexual and fathering an illegitimate child with a teenager. Segretti was one of several Nixon operatives who ended up in jail. Hide Caption 4 of 7 Photos: Political dirty tricks Political dirty tricks – Doctored photos?: Ross Perot was the first major third-person candidate in modern American politics to mount a serious run for the White House. His plainspokenness got attention, and his platform appealed to the far right. Most of all, he was seen as a threat to split the Republican vote with President George H.W. Bush, who was running for his second term. Despite the energy in his campaign, Perot dropped out of the race, claiming that Republican operatives were about to smear his daughter with doctored photos and try to ruin her wedding. Perot never explained what the photograph purportedly showed. Hide Caption 5 of 7 Photos: Political dirty tricks Political dirty tricks – The mystery of Alvin Greene: When Alvin Greene suddenly won the Democratic primary for U.S. Senate in South Carolina, experts asked, "Who?" Greene didn't campaign, had no political experience and was rarely seen in public. A CNN interview led to more questions of whether Greene, pictured, was intellectually capable of running a viable campaign. Others felt that Greene was planted by Republican Sen. Jim DeMint, who was running for re-election. Greene was cleared by the South Carolina Law Enforcement Division before he lost overwhelmingly to DeMint. Hide Caption 6 of 7 Photos: Political dirty tricks Political dirty tricks – Swift-boating: Before John Kerry, far right, was elected senator, he won the Purple Heart and a Bronze Star for his service in Vietnam and later protested against the war. When he ran for president in 2004, he spoke out against the Iraq War. Although Kerry was seen as the underdog in the race, he was gaining momentum before a political ad released by the group known as Swift Boat Veterans for Truth accused Kerry of speaking ill of his fellow veterans and lying to get his medals. Kerry first tried to ignore the ads before denying the allegations, but by then the ads -- and Kerry's avoiding them -- stopped whatever momentum was building. Hide Caption 7 of 7

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His performance during and after the October 2012 storm just before the presidential election has been widely praised and is a fundamental illustration of his straight-shooting political brand.

In the new investigation, federal auditors will examine New Jersey's use of $25 million in Sandy relief funds for a marketing campaign to promote tourism at the Jersey Shore, New Jersey Democratic Rep. Frank Pallone told CNN

In an August letter , Pallone asked the Department of Housing and Urban Development inspector general to look into how Christie chose to spend the marketing money approved by the department.

The inspector general's office confirmed the investigation.

Pallone wrote that he was concerned about the bidding process for the firm awarded the marketing plan; the winning firm is charging the state about $2 million more than the next lowest bidder.

The winning bid of $4.7 million featured Christie and his family in the advertisements while the losing $2.5 million proposal did not feature the Christies, Pallone said.

On Sunday, Pallone told CNN that the inspector general conducted a preliminary review and concluded there was enough evidence to launch a full-scale investigation into the state's use of federal funds.

The audit will take several months and the findings will be issued in an official report, he said.

Pallone, a 27-year veteran of the House and vocal Christie critic, said this is not about politics.

"This was money that could have directly been used for Sandy recovery. And, as you know, many of my constituents still haven't gotten the money that is owed them to rebuild their homes or raise their homes or to help," he said.

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Democrats slammed Christie over the summer for starring in taxpayer-funded ads as he was running for re-election in November, arguing it gave him an unfair advantage.

Christie aides said at the time that the winning bid provided more value.

In a statement on Monday, Christie's office said the "Stronger than the Storm" campaign was part of an "action plan" approved by the Obama administration and developed with the goal of showing that the New Jersey shore was open for business just several months after the storm.

"Federal agency reviews are routine and standard operating procedure with all federally allocated resources to ensure that funds are distributed fairly. We're confident that any review will show that the ads were a key part in helping New Jersey get back on its feet after being struck by the worst storm in state history," according to the statement issued in response to questions from CNN.

Last week, Christie dismissed two top aides for their apparent involvement in the closure of access lanes to the George Washington Bridge, which caused traffic nightmares for days in and around Fort Lee.

New Jersey legislators are investigating whether the aides -- a senior Christie staffer and a high-level appointee at the Port Authority of New York and New Jersey -- ordered the lane closures as political retribution. The U.S. Attorney in New Jersey also is looking into the matter.

Christie has said he didn't know about the alleged scheme and was "embarrassed and humiliated" by it.

Democrats in New Jersey and nationally have jumped on the scandal, saying it gives the nation a chance to see what they've said for years -- that Christie is a bully who governs by fear. His supporters say his swagger and frank nature convey confidence and have helped make him a successful governor.

But as bad as the bridge scandal is for Christie, any finding that he improperly spent Sandy aid would tarnish the signature achievement that has helped elevate his legacy and made him a serious potential challenger for the White House.

Sandy, a historic storm, pummeled coastal areas along the mid-Atlantic, knocking out power to millions, causing massive flooding and killing more than 100 people in the United States.

Parts of the New Jersey shore were devastated, but the state and local communities in many hard-hit areas rebounded surprisingly quickly and reopened their beaches last summer.

Christie and President Barack Obama toured one community in May to demonstrate the effectiveness of recovery efforts helped by billions in federal money that went to New Jersey and other states affected by the storm.