Paul Kane / The Washington Post

WASHINGTON — The U.S. Senate, once considered the most exclusive and chummy club in America, has in recent years been transformed into an ideological war zone, where comity and compromise have lost their allure, while confrontation and showmanship now pay big dividends.

“The only way you get something is to become obnoxious,” Sen. Mary Landrieu, D-La., declared during the recent immigration debate, explaining her threat to block the entire process. “We have turned from a Senate to a theater, and I’m tired of being part of a theater. If I wanted to be part of a theater, I would have gone to New York.”

The theatrics reached new heights Thursday when Majority Leader Harry Reid, D-Nev., and Minority Leader Mitch McConnell, R-Ky., confronted each other over Reid’s effort to change the filibuster rules in ways that would strip the GOP’s ability to block confirmation of executive branch nominees and that could ultimately weaken the minority party’s ability to slow the majority agenda.

Reid’s move provoked some of the most personal attacks two Senate leaders have leveled against each other in decades; Reid described McConnell as untrustworthy, while McConnell countered that the Nevada Democrat would go down in history as the worst Senate leader ever.

Suddenly, the world’s greatest deliberative body just isn’t that much fun anymore.

“I miss it like an abscessed tooth,” former senator Christopher Bond, R-Mo., a 24-year veteran, said on a recent visit to the Capitol.

The dysfunction fever is so strong that Reid and McConnell relented to a rank-and-file request to set up a rare meeting for senators of both parties Monday night in the Old Senate Chamber.

Those working at the last-gasp filibuster compromise fear that if they fail, the Senate will put itself on a permanent downward spiral later this week.

“There’s no doubt that it’s harder, and it’s more partisan,” said Sen. John McCain, R-Ariz., who has spent the past few days talking with senators and White House allies hoping to hatch a compromise on Senate rules. McCain has succeeded twice before at reaching a compromise to avoid partisan rule changes, first in 2005 and again this year.

Interviews with more than a dozen current and recently retired senators paint a mostly dismal picture of life in the Senate. There is a growing sense of despair among the rank-and-file senators, who privately grouse that the two leaders, despite many similarities in style and background, have become so mutually distrustful they barely speak to each other, except for small talk about their shared love of the Washington Nationals.

One GOP senator last week pleaded with McConnell to reach out to Reid to establish some regular channel of communication, maybe a biweekly breakfast, to try to solve their problems. McConnell declined, saying he simply could not trust Reid, according to the Senate Republican, who asked for anonymity to speak about the relationship.

Reid and McConnell are “institutionalists” who shared the same career goal — to be Senate majority leader. Reid has held that title since 2007; McConnell will probably need six additional Republican seats in the 2014 midterms to reach his lifelong prize. By those elections, they will have served as party leaders longer than any duo since Robert Byrd, D-W.Va., and Howard Baker, R-Tenn., in the late 1970s and early 1980s. Instead of growing closer, however, Reid and McConnell have grown more distant and distrustful of each other, according to senators on both sides of the aisle.

But in some way the Reid-McConnell clash is a symptom of other changes in the Senate.

In the past five years, through death and retirement, the Senate has lost a clutch of legends, powerful voices whose decades of service gave them enough influence to rival that of the leaders.

John Warner, R-Va., Edward Kennedy, D-Mass., and Ted Stevens, R-Alaska. These were Senate barons who could roll their own leadership when it was required to make a deal. Warner retired in 2008. Stevens and Kennedy died in 2009.

A treasured requirement for freshman orientation used to be a rules lecture inside the chamber from Byrd, the longest-serving senator ever, who wrote a book on parliamentary rules. But no senator has taken up that role since Byrd grew ill and died in 2010.

There has been a shift away from “senators who carried with them the sense of the history and the traditions of the Senate,” said Sen. Lisa Murkowski, R-Alaska, who arrived in 2003. “There was that class of senior senators that were accorded a great deal of respect and authority.”

They have been replaced by a historically large group of newcomers who are generally more partisan and have pushed leaders, their party and the Senate to a more combative footing.

In March, Sen. Dianne Feinstein, D-Calif., a 20-year veteran, bristled at freshman Sen. Ted Cruz, R-Texas, for what she described as his condescending tone during a debate about gun control, lecturing Cruz that she was not a sixth-grader. A week earlier, McCain, responding to a filibuster led by Sen. Rand Paul, R-Ky., against the confirmation of John Brennan as CIA director, called Paul and his younger libertarian-leaning Senate allies a bunch of “wacko birds.”

If there is any hope that better is possible, it comes from Sen. Timothy Kaine, D-Va. Six months into his first term, Kaine has been pleasantly surprised. In the past two months the Senate has approved, by large bipartisan margins, legislation to shore up the nation’s waterways, an overhaul of farm policy and a comprehensive immigration bill.

Each of those was approved after lengthy, freewheeling debate on amendments in line with Senate traditions. At this stage of 2011, the Senate had held only 106 roll-call votes; this year, 171. Yet some basics, such as the budget resolution, have ground to a procedural halt.

“The notion that we can’t work together on anything, I’m not finding that to be true,” Kaine said. “But I’m also finding things that ought to be simple are hard. It’s like parallel universes. I’m trying to understand how an institution can be both.”