Like many great love affairs, this one started late at night. Jim Manley fell for the Senate during the long evenings he worked after arriving on Capitol Hill in 1993.

The notorious workaholic recalls coming in early and staying well into the night. That’s when the building empties of tourists, when the only people left are Senators and staffers plotting out strategies and the reporters lurking in the hallways.

“Everybody knows the best stuff only occurs late at night,” says Manley, who plans to leave the Senate after 18 years, having served most recently as chief spokesman for Majority Leader Harry Reid (D-Nev.).

To Manley, 49, one of the most powerful aides on Capitol Hill, that “best stuff” is the stuff on which he has long thrived — the deal-making, the adrenaline, and always, the spin.

But for all his reverence for the institution, Manley is known among colleagues and reporters for never taking it all too seriously.

“He always got the absurdity of the place, even when it was melting around him,” says veteran New York Times reporter Carl Hulse. “He’s someone who really loves the culture, but you always knew he got the joke, whatever goofy thing had just happened.”

Manley and his House-side counterpart, Brendan Daly, spokesman for Speaker Nancy Pelosi (D-Calif.), often publicly jab one another. In private, though, they share many laughs about their cross-Dome one-upsmanship. “We’re always giving each other grief,” says Daly, who is also leaving the Hill.

In February, after a record-breaking snowfall sidelined Washington, Daly gave the following quote to the Wall Street Journal: “Recovering from this blizzard demands patience, cooperation, collaboration and teamwork. Unfortunately, the Senate is in session this week.” Afterward, Manley sent Daly a taunting e-mail.

The cross-Capitol parrying goes both ways. In Friday’s Wall Street Journal story on the tax bill, Manley dissed the House. “This vote demonstrates they may be irrelevant to this process,” he said of Daly’s employ.

Manley broke into a wide grin when recalling the quote.

For years, Manley has endeared himself to reporters by being accessible and honest. He’s known to return a BlackBerry message into the early morning hours and frequently makes loops through the press galleries, dropping by reporters’ desks to hammer home a messaging point. Often those visits are simply to casually dispense useful tips for reporters: his best guess on what time the chamber would adjourn, perhaps, or a heads-up on a floor speech Reid was about to deliver.

Not that there wasn’t tension between the spokesman and the spoken-to. Manley has yelled at reporters he thought were missing — or skewing — a point to the detriment of his boss; reporters often yelled back. But he doesn’t hold grudges, many scribes note. “I would go to the mat to defend a position, but then you leave it at that, you wake up, and today’s another day,” he says.

Manley’s prolific use of profanity also ingratiated him with journalists, who are known for salty language and tend to respect those who swear creatively. Manley admits that he might be most mourned once he leaves the Hill by the staffer who keeps a “swear jar” in Reid’s office. Staffers throw money into it after they drop expletives. “My support will be missed,” he says.

For all his collegiality with the press, Manley still sees the media as the opposition. Asked how he defines his job, he answers forcefully in the language of defense. “My job is to protect Sen. Reid and our caucus,” he says.

Working His Way Up

Politics was part of Manley’s life growing up in St. Paul, Minn. His grandfather was a prominent member of the Democratic-Farmer-Labor Party, Minnesota’s Democratic organization, and served in the state Legislature for years.

After graduating from the University of St. Thomas in St. Paul, Manley worked for a law and lobbying firm, and then he moved to the center of the political universe, Washington, D.C. Friends who worked for the Minnesota delegation helped him land his first job, as a press assistant to former Senate Majority Leader George Mitchell (D-Maine).

Most of Manley’s years on the Hill were spent working for Sen. Edward Kennedy, handling press for the Massachusetts Democrat’s Health, Education, Labor and Pensions Committee and acting as Kennedy’s personal press secretary. Kennedy was known for hiring top-notch staff, a fellowship of whip-smart overachievers.

Even among this elite group, Manley’s zeal for long hours and hard work impressed. “Sen. Kennedy was hard-charging, and he set the pace for the staff,” says Michael Myers, a longtime senior Kennedy aide who is now with the Rockefeller Foundation in New York. “Jim earned his respect by being a hard worker.”

Adjusting to Kennedy’s style wasn’t easy. The first time Manley’s name appeared in a local Massachusetts paper, Kennedy was irate. “He read me the riot act,” he recalls. “He asked, ‘How many times have you been elected to the U.S. Senate?’ I learned my lesson.”

But when Reid tapped Manley to join his leadership office in late 2004, the Nevada Democrat wanted a far more vocal spokesman. Reid, then the Minority Leader, hired Manley to head the “war room,” a press operation that was supposed to respond, quickly and emphatically, to attacks, particularly those from the George W. Bush White House, and to launch bombs of its own.

Manley’s role was to play the heavy, allowing Reid to keep his hands clean.

His job, though, was sometimes complicated by his boss’s propensity for verbal blunders, which ranged from the politically damaging to the merely cringe-worthy — and they frequently launched Manley into high-spin mode.

In 2005 Reid called Bush a “loser” and a “liar” during a speech at a Nevada high school. And then there were the amusing gaffes. In 2008, for instance, Reid peppered remarks about the newly opened Capitol Visitor Center with a gratuitous aside about how tourists visiting the Capitol smelled badly.

Manley calls his boss “plain-spoken” and acknowledges that his bluntness sometimes presented a challenge. But “I thought speaking your mind was a virtue,” he says.

Reid grew to trust his aide and now calls him a friend whom he’ll miss dearly. “I’ve worked with a lot of press people in my career, but you’re rarely around someone as knowledgeable as Jim Manley,” Reid says. “He has the best contacts with the press I’ve ever seen.”

Members of the Democratic Conference say they appreciated both Manley’s aggressive public stances on their behalf and his easygoing demeanor behind the scenes.

“He’s tough, but he’s got soft edges,” says Sen. Patty Murray (D-Wash.). “He’s conscious of relationships — with us, with the press — and that’s served him well.”

Goodbyes Are Bittersweet

The Senate has ruled Manley’s schedule for the better part of two decades. Although he loves the institution, it can be a cruel mistress.

After the Nov. 2 midterm elections, Manley faced a thinner Democratic majority and a reshuffled communications staff, so he decided it was time to leave. He attributes his departure to burnout, curiosity about life beyond the Senate and a desire to make more money.

“If I’m going to take my job seriously, which I do, I had to leave,” he says. “I’m not going to do anything half-assed.”

Still, his imminent departure has him feeling nostalgic. Sitting in the ornate Senate reception room, Manley recalls the Kennedy years, being on the floor for the historic health care vote, the honor of speaking for the Senate Majority Leader.

“I was Sen. Kennedy’s pooper-scooper,” he says, referring to cleaning up after Splash and Sunny, the late Senator’s Portuguese water dogs. “I’ve met prime ministers and presidents and rock stars and movie stars. … I’ve watched legislation being made.”

He is uncharacteristically Zen about his job prospects.

“I’m keeping an open mind. I’m listening to everything. I’m trying to think outside the box, and I want to think big.”

Manley still has yet to set the date of his departure. Perhaps he’s avoiding the bittersweet reality that his days as a Senate employee really are over. But mostly, it’s a logistical problem. There is a tax cut bill to finalize, reporters’ calls to take, messages to craft.

“I’m going out swinging,” he says, checking his BlackBerry reflexively. “I’m working so hard, I don’t have time to look for a job.”