John Isner and Nicolas Mahut completed the longest match in tennis history Thursday. Isner won the monumental fifth game by the staggering score of 70-68 during a saga strung out over three days at Wimbledon.

But Isner and Mahut have nothing on the epic battle waged between House and Senate negotiators to forge a final version of a massive financial re-regulation bill. The ultimate negotiating session wrapped up at 5:39 this morning after lawmakers bargained for more than 20 hours in Room 106 of the Dirksen Senate Office Building.

The legislation imposes some of the toughest regulatory reforms in 80 years, creates consumer protection measures, shields some borrowers from special costs and eases lending.

You think Isner and Mahut have stamina? I’d like to see that duo try to break service in a doubles match with House Financial Services Committee Chairman Barney Frank (D-MA) and Senate Banking Committee Chairman Chris Dodd (D-CT) at Centre Court.

When the House and Senate approve competing versions of the same bill, lawmakers must select between two options to reconcile their differences. They can either play Ping-Pong or hash things out in a conference committee.

Ping-Pong is where the sides bounce the legislation back and forth between the two chambers. Each makes alterations until they have synched up the legislation in a final bill.

The House and Senate didn’t engage in Ping-Pong when they went to iron out differences on the massive, financial re-regulation bill. They chose the conference committee route. That’s where lawmakers from both bodies negotiate around a table, bartering proposals until they craft a unified package to be presented again to their respective chambers.

And even though the House and Senate eschewed Ping-Pong for a conference committee, they wound up playing tennis instead.

At least the type of tennis stylized by Isner and Mahut at Wimbledon.

Frank and Dodd launched the conference committee two weeks ago. But Thursday was the grand finale. They were going to be there as long as it took. Whether they got to match point or not.

Around 4:30 pm Thursday, I asked Rep. Spencer Bachus (R-AL), the leading Republican on the House Financial Services panel, how long he thought the session would go.

“I’d say we’ll wrap it up around 8 or 8:30,” Bachus said. “It’s going rather well.”

At 11:06 pm Thursday, the green, tile hallway outside 106 Dirksen buzzed. Lobbyists, Congressional aides and Treasury Department officials lurked in the corridor. Some huddled in caucuses at the side, clutching binders to their chests and speaking in hushed tones. Others sipped soda from McDonald’s paper cups. Another chewed on animal crackers. Reps. Michael McMahon (D-NY) and Melissa Bean (D-IL) found Rep. Scott Murphy (D-NY) around the corner and talked with him near a cleaning cart left in the corridor by a member of the custodial staff. Sen. Chuck Schumer (D-NY) emerged from the meeting to take a cell phone call.

The shorthand and alphabet soup of acronyms people spoke in was nearly indecipherable to the untrained ear.

“Who would have thought the CFPA would be an afterthought,” mused one Congressional aide.

“The GSE Fannie and Freddie stuff is driving me nuts,” lamented a lobbyist.

“What about the de minimus value on the Volcker Rule?” queried another.

To the uninitiated, let’s interpret these ciphers by running them through the Congressional, inter-galactic translator.

The CFPA stands for the controversial Consumer Financial Protection Agency which would regulate much of the business community. GSE is an acronym for “Government-Sponsored Enterprise.” Those are institutions crafted by the government like Fannie Mae and Freddie Mac. Fannie Mae and Freddie Mac are chartered by the government to purchase mortgages and sell them to investors. The “Volcker Rule” is named after former Federal Reserve Chairman Paul Volcker. The Volcker Rule bans banks from making investments that have nothing to do with their customers.

Some of the corridor jockeying was akin to getting scouting reports on a fantasy football team.

“There’s a provision about clearing houses,” said one man to another in a thick, pin-stripe suit. “We like that.”

“That’s good language,” said one man to another, showing him a message on his BlackBerry screen.

Then a man in glasses emerged from the hearing room only to be buttonholed immediately by a man who just came around the corner.

“If they want our vote, you’ve got to show it,” implored the second man.

“If I can do it, I will. But I can’t promise you anything,” said the first, and briskly walked away.

But many episodes weren’t nearly as intense. Some aides roamed the halls with bloodshot eyes. Downstairs, a woman squeezed a few quarters into a vending machine and stared blankly at it for a good two minutes before making her selection (Knott’s Berry Premium Raspberry Cookies).

“I really feel like I’m losing it,” said one male staffer sporting a loosened tie. “It’s like I’ve been out drinking. I feel so loopy.”

At 11:38 pm, an aide bolted out of an anteroom and sprinted frantically down the hall, destination unknown.

The inside of the conference committee hummed as people held discrete conversations around the edges of the room. Meantime, lawmakers slogged through amendment after amendment and proposal after proposal.

The lawmakers sat around a gigantic set of tables that were arranged into a square and draped with a white table cloth. House members were on one side and faced senators positioned on the other. Aides roamed the dais. Reporters operated along the sides of the room, hunched over laptops. Reams of paper were strewn about the floor. Some pages were copies of amendments, stained with coffee. A number of people unearthed electrical outlets at the rear of the room and powered their PDA’s, long-ago drained of juice.

Reps. Collin Peterson (D-MN), Leonard Boswell (D-IA) and Ed Towns (D-NY) sat at the table and listened. Each had removed their suit jacket. Meantime, Reps. Henry Waxman (D-CA), Elijah Cummings (D-MD) and Mel Watt (D-NC) kept theirs on as Barney Frank presided over the conclave.

“Do all members have the amendment?” asked Frank of the latest proposal. “We’ll withhold until we do.”

At that, a woman darted out of the room. Someone rapidly passed copies of the amendment around the table. The cacophony created by the clicking of multiple staplers sounded like a team of woodpeckers operating in slow motion.

The conference committee slogged on. Just as it had done for days as lawmakers plowed through proposals to exempt automobile dealers from the new regulations and amendments about derivatives.

What’s interesting is that these drawn-out, tedious conference committees used to be the way the House and Senate resolved most of their differences. Certainly, there have been “show” conference committees in recent years. That’s where everything is already agreed upon. Or the majority side just rolls the minority. Such was the case in the winter of 2009 when House and Senate negotiators met in a conference committee on the $787 billion economic stimulus package. Lawmakers pretty much gave brief statements either endorsing or denouncing the bill. And that was it.

This was a real conference.

“We need to do it more often,” said Rep. Elijah Cummings (D-MD), one of the House conferees. “It’s a time-consuming process. Which is why we haven’t done it in the past.”

Fellow conferee Rep. Bobby Rush (D-IL) agreed with his colleague.

“It reminded me of the good ol’ days,” said Rush. “There’s nothing like the give and take between the House and Senate.”

Partisanship has intensified in recent years in Congress. That’s the main reason lawmakers have ditched earnest conference committees and carved agreements in back rooms.

The health care reform debate piqued the interest of the public like no other in recent years. After the House and Senate passed vastly different versions of the legislation, many pined for an open conference committee. But Democrats argued privately that a conference committee on a bill of that magnitude would have been interminable. And Senate Republicans didn’t allow Democrats to appoint conferees or move to go to conference.

The point about conference committees is this: when it’s a real, open conference like the financial regulation bill, it can be one of the most numbing, stultifying processes you’ve ever seen. Big money was at stake on this legislation. But only people with the most-granular knowledge of these issues could follow the action. Especially when the conference dragged past midnight.

“This was reinvigorating. It was therapeutic,” Rush said of the conference committee when I asked him about it around 6:30 Thursday night.

Of course, one may wonder if Rush would choose those same words when Barney Frank closed the conference committee at 5:39 am Friday morning.