The world’s greatest deliberative body has started to look a lot like its legislative little brother over the past few years.

The Senate was once regarded as the home of the great political orators of the time — not to mention the body where true dealmaking actually took place. Its members prided themselves on their cool approach to legislating, in contrast with the more brawling nature of the House. Senators, generally, liked one another — no matter their party — and weren’t afraid to show it, either personally or politically.

No longer. The Senate has undergone a marked transformation, symbolized by increased partisanship, blockading for the sake of blockading and even some downright personal nastiness.

A few examples:

First, the partisanship. According to Yahoo’s Chris Wilson, who last month broke down each senator’s votes up to that point in 2013, 22 Democratic senators had voted the exact same way on every single piece of legislation that had come before the chamber. When examining the senators who had voted together at least 75 percent of the time, Wilson found only two moderates who bridged the middle ground between the two sides: Sens. Susan Collins (R-Maine) and Lisa Murkowski (R-Alaska). Sens. David Vitter (R-La.) and Frank Lautenberg (D-N.J.) were genuine outliers, having voted with no other senator — of either party — at least 75 percent of the time this year.

Then, the blockading. As The Post’s Juliet Eilperin noted in a Fix post last week, there are currently 15 judges nominated by President Obama awaiting votes by the full Senate. Thirteen of the 15 — or roughly 87 percent — of those nominees were approved unanimously by the Senate Judiciary Committee. And even those who get votes often have to wait forever for them. On March 11, for example, the Senate confirmed Richard Taranto for the U.S. Court of Appeals for the Federal Circuit by a vote of 91 to 0, 484 days after the president nominated him — and he’s far from the only example of that trend.

And, finally, the nastiness, which may be the most striking break from the old ways of the Senate. Take Ted Cruz, the newly installed Republican senator from Texas. In his first three months in Congress, Cruz has clashed with everyone from Sen. John McCain (an Arizona Republican who referred to Cruz and a few other tea-party-aligned Republicans as “wacko birds”) to Sen. Dianne Feinstein, the California Democrat who, after Cruz questioned the constitutionality of gun legislation she backed, scolded him by replying, “I’m not a sixth-grader.”

Former Louisiana senator John Breaux (D), a noted moderate who retired from the chamber in 2004, blamed the Senate’s changed atmosphere on several factors.

“Large numbers of senators are former House members and try to turn the Senate into a tightly structured second House,” Breaux explained. “They get over that after a couple of years, as I did, but the turmoil it creates can cause dysfunction. Add to that a fewer number of centrists from both parties, and we have the difficult situation we see today.”

Nearly half of the Senate — 26 Democrats and 22 Republicans — served in the House either directly before being elected to their current job or at some previous point in their careers in elected office.

(Worth noting: Cruz as well as Sens. Mike Lee of Utah and Rand Paul of Kentucky — a Republican trio who have wreaked considerable havoc in the Senate this year — did not serve in the House before being elected to the upper chamber.)

What’s perhaps more telling than the number of House members now in the Senate is the sheer newness of the vast majority of the body. Six years ago, 44 senators had served at least three terms; today that number is 32. At the start of the 113th Congress, more than half of the senators had served one full term or less.

Deaths (Ted Kennedy, Robert Byrd, Daniel Inouye) and defeats (Dick Lugar, Bob Bennett) over the past few years have contributed to a loss of old bulls — and institutional wisdom — the likes of which the Senate hasn’t endured in generations. And some pending retirements (Jay Rockefeller, Carl Levin, Tom Harkin) will only continue the trend.

That the Senate is a different — more partisan, less collegial — place than it was even a decade ago has taken a toll on its membership. Sen. Olympia Snowe (R-Maine), who shocked the political world by retiring in 2012, acknowledged that changed reality bluntly in an op-ed for The Post roughly a year ago. “The Senate is not living up to what the Founding Fathers envisioned,” she wrote.

Not all is lost, argued Ted Kaufman, a longtime aide to then-Sen. Joe Biden (D-Del.) who succeeded him as senator from 2009 to 2010.

“We experienced in the 112th Congress a unique period where the House was taken over by a hyper-partisan Republican Party,” Kaufman said. “The results of the last election are already mitigating that.”

Maybe. The next few months will put the Senate’s identity to the test as immigration, guns and the budget — all of which have deeply divided the chamber of late — will come up for votes. Will it define itself as a second House or truly the “upper chamber”?

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