For a man at the center of a wide-ranging federal investigation into a vast shadow campaign prosecutors say helped Mayor Vince Gray win the 2010 election, Jeff Thompson sure doesn’t look too worried.

At least he didn’t two weeks ago, when he sat for a lengthy deposition as part of an ongoing legal battle over a real estate deal gone bad.

Thompson, a D.C. Medicaid contractor and accountant, looked like he was enjoying himself as he sparred for hours with the attorney who is suing him over a failed bid to purchase a Capitol Hill building. Thompson cracked jokes about his inability to use email, boasted of his business acumen, and let it be known that he’d just paid $300 for a hair cut, manicure, and pedicure.

Not bad for a guy on the hot seat. And make no mistake, that’s definitely where Thompson sits. In March, the feds raided his house and former accounting firm’s office, seizing millions of documents (along with Thompson’s personal iPhone). U.S. Attorney Ron Machen and his team have already laid out a considerable portion of a potential case against Thompson. Based on information from sources familiar with the investigation and details and comments in court records and testimony, Thompson is the unindicted “co-conspirator #1” who the feds say was the money man behind an alleged $650,000 off-the-books shadow campaign and $44,000 worth of straw donations to the Gray campaign.

But Thompson looked like he had few cares in the world as he dueled with attorney Charles Parsons over a Capitol Hill building that’s home to Ian’s Hair Studio. Parsons says in court filings Thompson improperly reneged on a deal to sell because Ian Thorne, the hair salon’s namesake, didn’t like the price to which Thompson and Parsons agreed. Thompson says he never agreed to sell the property to Parsons.

For much of the deposition, a relaxed Thompson laughed at his own jokes and almost seemed to be enjoying himself as he went back and forth with an excitable Parsons.

When asked whether he knows of the whereabouts of the Capitol Hill property’s previous owners, Thompson replied:  “I don’t know where they are, if they are in Timbuktu or Mars or Jupiter. Why don’t you check that out?”

And when Parsons asked whether one of Thompson’s old real estate partners, Kweisi Mfume Jr., is the son of the former Maryland congressman and former head of the NAACP, Thompson did his best to needle Parsons.

Q: Is Mr. Mfume related to the congressman?

A: Why don’t you go ask him?

Q: I am asking you.

A: I don’t know. Why don’t you go ask him?

Q: You have no idea?

A: Why don’t you go ask him?

After a spat between Parsons and Thompson’s attorney, Thompson said: “I think that is his son. You know that….Be humorous.” He then suggested Parsons have a glass of wine.

When Parsons interrupted Thompson later on, Thompson suggested he get “Q-Tips and clean” out his ears.

Thompson showed his generous side too, explaining in the deposition how he’s allowed Thorne to use the building rent-free since he bought it 12 years ago and how he wants a portion of the proceeds from its sale to go to Thorne’s son, who is also Thompson’s godson. Thompson said he gives Thorne money when Thorne asks for it “from time to time.” (Thorne, who campaign records show is a frequent contributor to local politicians, could not be reached for comment. Nor could David Wilmot, one of the city’s highest paid lobbyists, who Thompson said in the deposition once represented Thorne in a contract matter.)

In total, the three-hour video of the deposition, which Parsons provided to LL, provides a rare glimpse into the personality and temperament of the man at the center of the tempest that’s engulfed the Wilson Building.

Thompson has been one of the heftiest tunas in city politics for more than a decade. After coming to D.C. as a 20-year-old from Jamaica in the 1970s, Thompson got an accounting degree from the University of the District of Columbia and built an empire that at its peak included the largest minority-owned accounting firm in the country, a Medicaid contract worth more than $300 million a year, and a tidy local real estate empire. At one point, Thompson owned five homes in D.C., including two Crestwood estates each worth more than $1 million; the hair salon building; a $2 million plot of land on Poplar Point; and a prime downtown building (assessed at $6 million) where his health care company has a lucrative lease with another company owned by Thompson.

Associates say Thompson is the consummate entrepreneur, always on the lookout for a good deal. And city contracts have proved to be a great deal for him. He leveraged his close relationship with former Mayor Anthony Williams to become one of the city’s biggest health care contractors. His Medicaid company, Chartered Health, had a string of very lucrative years until the city sued it for allegedly overbilling, which ended with Chartered paying the District a $12 million settlement in 2008 (though the company did not admit wrongdoing).

Thompson and his associates have been a significant source of D.C. campaign cash for more than a decade, giving at least $830,000. That only includes contributions LL was able to tie directly to Thompson or his associates through business, court, or other records, so it may vastly understate the real amount.

Still, Thompson has kept an amazingly low profile, which is why the deposition video is such a rare glimpse of him. A Nexis search for “Jeffrey E. Thompson” shows that he was only mentioned five times in passing in the Washington Post prior to last year, despite his years of influence. His profile has been even lower since the FBI raids in March, and his defense attorney, Brendan Sullivan, has made virtually no public comments.

The feds indicate Thompson has known he’s been in their sights for more than a year. Last August, “co-conspirator #1” tried to ship off one of his associates, Jeanne Clarke Harris, to Brazil to stymie investigators, court records say. In December, the feds say in court papers, “co-conspirator #1” ordered Harris, who has pleaded guilty to various campaign fraud charges, to file bogus tax documents in an effort to cover their tracks.

Meanwhile, Thompson’s business empire has been in steep decline, and he’s become a pariah to the local and national candidates who have accepted his money (President Barack Obama‘s campaign and the Democratic National Committee have returned $10,000 worth of Thompson donations, and Maryland Gov. Martin O’Malley gave about half of the nearly $80,000 in Thompson-related contributions his campaign has received to charity). Thompson sold off his interest in his accounting firm in July, and he’s trying to sell Chartered, which the city says will likely not win any more contracts with Thompson at the helm.

As for the Capitol Hill property at issue in the lawsuit with Parsons, Thompson listed it for sale last November, as he began selling off some of his assets. He initially priced it at $700,000, then dropped the price to $500,000 in December. By February, it was down to $400,000, and Thompson was entertaining offers as low as $382,500, according to court records.

In fact, that steady downsizing of his empire may be taking a toll on Thompson. The moments in the deposition when Thompson loses his cool came when Parsons suggested that he was under duress when he tried to sell the property.

“What do you mean by sense of urgency?” Thompson snapped at Parsons. “My decision to sell it.” He repeated that the sale was “my decision” another three dozen times.