Here’s an irony the Founding Fathers could never have anticipated: The old-fashioned filibuster — that most archaic of parliamentary tools — is suddenly the rage of the attention-span-challenged social media set.

Sen. Rand Paul (R-Ky.) created a sensation Wednesday by railing for nearly 13 hours straight in the Senate chamber against the Obama administration’s use of unmanned drones.

The freshman senator lost on the question at hand, as pretty much everyone expected he would. The Senate approved the nomination of John O. Brennan to lead the CIA on Thursday on a vote of 63 to 34.

But Paul’s speech won praise from the civil libertarians on the left and the right. Twitter tracked 1.1 million tweets relating to the filibuster, 450,000 with the hashtag #standwithrand.

Many conservatives noted that Paul and a few allies were tenaciously holding the floor even as a group of fellow Republican senators was committing the heretical act of dining with President Obama across town.

Paul’s speech, believed to be the ninth longest in Senate history, also drew plenty of criticism.

“The country needs more Senators who care about liberty, but if Mr. Paul wants to be taken seriously he needs to do more than pull political stunts that fire up impressionable libertarian kids in their college dorms,” the Wall Street Journal wrote acidly in an editorial that Sen. John McCain (R-Ariz.) read Thursday on the Senate floor.

Either way, Paul had found a means both retro and fresh to draw attention to himself and his issue. “It was a great day in the history of the United States Senate that Rand Paul breathed life into a procedure that many people believed had been bypassed by time,” said Ross K. Baker, a Rutgers University political scientist.

Sen. Bernard Sanders (I-Vt.) discovered the same thing in 2010, when he spoke for more than eight hours against a tax-cut plan that Obama and Republican leaders agreed on.

“The social media was extraordinary. The Senate server broke down,” Sanders said in an interview Thursday, although he added: “The conventional media was not impressed.” Sanders’s speech was even published as a book.

That is because it was something rarely seen in recent years — the old-fashioned kind of filibuster that people associate with the iconic 1939 movie “Mr. Smith Goes to Washington,” in which an idealistic young senator played by James Stewart talks until he collapses.

The filibuster is as old as the Senate itself. The first one, in 1789, blocked a bill that would have located the nation’s capital on the Susquehanna River. It was famously employed in the 1950s and ’60s to slow down civil rights legislation.

As measured by the number of times cloture motions are filed to cut off debate in the Senate — 115 in the 2011-12 Congress — the filibuster is a more routine occurrence than ever. Efforts to streamline Senate procedures and discourage its use have failed, largely because the party in the majority knows that it may one day end up in the minority, and wants to protect the power to gum up the works.

But anyone who drops by the Senate during what passes for a filibuster in the modern era is likely to find a chamber that is almost vacant, the silence punctuated only by the voice of a clerk slowly calling the names of absent senators — the filibusterer himself usually among them.

What might be called the pseudo-filibuster was a convention that began during the 1970s, when the Senate was growing increasingly partisan. With a lot of business on the agenda, then-Majority Leader Mike Mansfield (D-Mont.) began opting to set bills aside in the face of a filibuster threat when he knew he the lacked 60 votes he needed to overcome it, rather than wasting time on doomed legislation.

One such “silent filibuster” is underway against the nomination of Caitlin Halligan to the U.S. Court of Appeals for the District of Columbia Circuit.

Only rarely does the majority party force the minority to execute a filibuster, which requires keeping a quorum of at least 51 in the chamber.

During a 1988 filibuster over campaign finance reform, for instance, then-Majority Leader Robert C. Byrd (D-W.Va.) dispatched the sergeant-at-arms with warrants for the arrest of absent Republicans. Sen. Bob Packwood (Ore.) had to be dragged into the chamber.

For all the acclaim that Paul received, “there’s less here than meets the eye,” said Thomas E. Mann, a congressional expert at the Brookings Institution.

He noted that Washington was pretty much shut down under the threat of snow, and that Majority Leader Harry M. Reid (D-Nev.) had no other business he needed to get done, “so why not let [Paul] talk. It had no material effect on things.”

But Norman Ornstein, a scholar at the American Enterprise Institute and a frequent collaborator with Mann, suggested that Paul’s achievement was outside the chamber.

Although few people probably spent hours listening to the filibuster, “plenty of people paid more attention to 10 or 15 minutes of Rand Paul than they did to anything in the Senate for a long time,” Ornstein said. “What it reflects is that in the Twitter era, people also hunger for something that takes some time and gives them depth.”

And even Reid had good things to say about Paul.

“This can be a Senate where ideas are debated in full public view — and obstruction happens in full public view as well,” he said. “Or it can be a Senate where a small minority obstructs from behind closed doors, without ever coming to the Senate floor.”

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