In need of a new roommate 22 years ago, Charles E. Schumer (D-N.Y.) persuaded his housemates to turn to his friend from Illinois, Richard J. Durbin.

They had already served 10 years together in the House, and Durbin was part of their rat pack of Democrats who agitated their leadership by day and convened dinner parties by night. As roommates in then-Rep. George Miller’s townhouse, Schumer and Durbin cemented a partnership that now spans more than three decades, including the past 10 years as the top lieutenants to Senate Minority Leader Harry M. Reid (D-Nev.).

The Schumer-Durbin friendship has recently fallen on hard times in a scenario unimaginable to some of their friends, but one that may have been predictable given their mutual ambition.

Reid announced recently that he would retire at the end of 2016, and even before that news was public, Durbin threw his support to Schumer as the next Democratic leader in what should have been a quintessential moment of friendship for two people who have been so close.

Durbin pulled Schumer off the Senate floor for a post-1 a.m. conversation and ended five years of what was widely perceived as a shadowboxing match to succeed Reid. “We’ve had a lot of good times together, we’ve had some differences, but I think you’ve earned this,” Durbin told Schumer, according to Durbin’s account.

Schumer wept.

Since that embrace, however, the two friends have been disputing who said what next during the fog of an overnight voting session. Durbin claims Schumer agreed to support his effort to remain in his current post as the Senate’s No. 2 Democrat, the whip. Schumer asserts that in their emotional discussion no specific deals were made.

Within days, their staffs broke into open feuding and accused each other of lying. A brief phone call between Schumer and Durbin attempted to patch things up, but they only thing they could agree on was to stop talking about the matter publicly.

The public silence of Sen. Patty Murray (D-Wash.) — the third wheel in the drama — has only thickened the plot. Murray is a potential competitor to Durbin who could become the first female senator to hold the whip post. In the past week, she ducked questions about her own aspirations.

At a leadership news conference Tuesday, Reid tried to shield his feuding understudies. “There’s never been a better leadership team in the history of this country,” Reid said, declining to address the dispute.

It’s left open the possibility that Senate Democrats, who are almost genetically averse to divisive party leadership races, could be on the verge of a pronounced battle between Durbin and Murray that would last nearly 20 months. The ideological balance would barely change, as both are avowed liberals, but such a campaign would turn largely on personalities and friendships.

And it could cause long-lasting damage to one of the Capitol’s most storied friendships, Schumer and Durbin, who leaned on each other in their slow rise from the back bench of the House to the front row of the Senate.

Both senators have pledged not to let this dispute ruin their decades of friendship. “It’s going to stay good,” Schumer said in a brief interview.

Longtime friends cannot believe it has gotten to this point. “I assume in the end they’ll work everything out. They’re good friends,” said Martin Russo, the former congressman from Illinois who has known them since the early 1980s. “In the end it’s all gonna work out. There’s a lot of noise out there for no reason.”

Russo served as a rabble-rouser for that clutch of young Democrats elected in the post-Watergate era. There was the regular Tuesday night dinner somewhere on Capitol Hill in which lifelong bonds were formed. The group included Schumer and Durbin; then-Rep. Barbara Boxer (D-Calif.), now in the Senate; then-Rep. Leon Panetta, long before becoming White House chief of staff, CIA director and secretary of defense. Rep. Nancy Pelosi (D-Calif.) joined the crew after winning a 1987 special election.

The focal point for many of the young Democrats became Miller’s townhouse on D Street SE, where the California Democrat’s family never moved in with him as originally planned. After a snowy 1981 night in which Russo couldn’t get home to the suburbs, he stayed at Miller’s house and immediately loved two-block commute.

He and Panetta decided to move in; they just needed a fourth.

One night, Schumer, a first-term lawmaker, returned to his cramped apartment to discover his things missing. A note taped to the door told him where to find his stuff: in Miller’s house.

The quartet broke up in 1992, when Russo lost his seat and headed for K Street. After President-elect Bill Clinton tapped Panetta to serve as budget director, government ethics officials said it would be a “conflict of interest” for a Cabinet-level officer to pay rent to a member of Congress, Russo said.

Amid the shuffle, Durbin became the natural choice to move in.

At this juncture, the course of the legend diverges, depending on whom you ask: One version says Durbin agreed to move in only if he could get an upstairs bedroom to himself. Another version has Schumer choosing to stay downstairs in the living room because Miller charged less rent to those without their own rooms.

Either way, the Schumer-Durbin bond grew stronger during the roommate years. Most late-night discussions centered on politics, policy and Capitol intrigue, but the roommates also saw their personal lives become very intertwined.

When Schumer’s young daughter was asked on a date, he turned to his roommates for advice. (Let her go out, but only on a group date with other children.) When Durbin’s daughter moved to Brooklyn, Schumer pedaled his bike to the neighborhood to make sure it was safe. (It wasn’t, so Durbin’s daughter moved to a better location.)

All this is why it seems hard to believe such close friends could get crosswise over such an important conversation about their political futures.

Early on March 27, during a marathon session on the Senate floor, Durbin figured out that Reid would announce later that day his plan to retire after 2016.

Durbin decided to cut off speculation about whether he would challenge Schumer. In an interview with The Washington Post later that day, Durbin described his talk with Schumer.

“I think you can be a good leader,” Durbin told Schumer, “and I want to be a part of that team and help you be successful for yourself, for the caucus, for the Democrats.”

The two shook hands.

Durbin’s allies say that in the actual discussion he precisely asked to keep his current post. But Schumer’s allies contend that Durbin never specifically asked to remain whip and that Schumer never offered.

“Senator Schumer made no commitments but regardless, he considers Senator Durbin a close personal friend,” Matt House, Schumer’s spokesman, said in a statement.

Durbin responded by openly campaigning to keep his job, which would come in a vote by Democrats after the 2016 elections. Murray has publicly called for detente, but privately there are signs she is testing the waters on a challenge to Durbin.

It’s left Democrats spun around, calling for their leaders to “chill out,” as Sen. Diane Feinstein (D-Calif.) recently put it .

“All of this is a year and a half away, almost two years away. So, why is this going on now?” Feinstein said this past week in an interview.

Five years ago, when Reid’s reelection looked difficult, the caucus swirled over a possible Durbin-Schumer race. But Reid made the discussion irrelevant by pulling away and winning reelection. The friends did not let the rampant speculation get to them.

“I’ve never seen any animosity on display,” said Sen. Lindsey O. Graham (R-S.C.), a frequent negotiating partner with both Democrats. “I’ve never heard either one of them say a bad word about the other when they’re not in the same room.”

A decade ago, the big tension came between Reid and Durbin, because Reid had served as whip for six years before Durbin. They quarreled over Durbin’s focus — he didn’t park himself on the Senate floor for parliamentary drudgework the way Reid did. Those early disputes created an opening for Schumer to grow close to Reid, becoming the leader’s closest confidant, according to several current and former senior aides.

Back then, Schumer successfully ran the campaign committee, delivering a majority in 2006 and then a short-lived filibuster-proof majority in 2008. He still receives credit for the big majorities that led to the passage of the Affordable Care Act, the rewrite of Wall Street regulations and a massive economic stimulus package.

Those successes gave Schumer the inside track to succeed Reid, and even Durbin seemed to realize it. His confidants suggest that the biggest decision Durbin made in recent years was to run for reelection in 2014 rather than retire.

Durbin won another six-year term, and Schumer is running in 2016, but no matter what happens in their leadership dispute, one thing is forever gone: They aren’t roommates.

Miller retired in January and sold his home. The longtime friends decided it was time to go it alone.

“After 22 years in the same spot, I told him: America will never be the same, but it’s time to move on to another living arrangement,” Durbin said.