Kentucky Republican Sen. Rand Paul has emerged from his 13-hour filibuster as a national political leader, having unexpectedly unified divergent wings of the Republican Party on the issue of civil liberties.

For libertarians, Paul's filibuster — and the groundswell of support for it across the conservative spectrum — was a crowning moment, signaling their reintegration into the mainstream Republican Party, which has largely dismissed, and even mocked, libertarian notions about civil liberties in the decade since the Sept. 11 terrorist attacks.

"This was a very big deal. In 36 hours, the Republican Party has completely changed," said Brian Doherty, a senior editor at Reason magazine who has been covering the Paul movement for two decades.

Brian Doherty. Business Insider "You literally saw the shift happen over the course of the day," Doherty said. "It started with Rand Paul, and then it was just [Sens.] Mike Lee and Ted Cruz. And then you had people like Marco Rubio and Saxby Chambliss joining in. And by the end of it, [Republican Minority Leader] Mitch McConnell was on the floor saying he was going to block [CIA Director John] Brennan's confirmation, and [RNC Chairman] Reince Priebus was tweeting that Senators should go join Rand Paul."

"Who knows, maybe in two years, the filibuster won't seem like a big deal," he added. "But today, it feels like everything has changed. Today, it feels like the Republican Party is different."

Doherty conceded that, for some conservatives, the embrace of Paul's civil liberties argument may be chalked up to antagonism toward the Obama administration. But, he added, "if that's what it takes to get Rush Limbaugh to say that he agrees with Rand Paul, that he's open to these ideas, I'll take it."

Paul's 13-hour stand on civil liberties also solidified his standing among the more purist fans of his father, Ron Paul, who have long been skeptical of the younger Paul's dedication to the Movement.

Take Justin Raimondo, the editorial director of the ultra-libertarian blog antiwar.com, who has been warning libertarians about Rand Paul since at least 2010. In a recent post following Paul's January trip to Israel with evangelical leaders, Raimondo accused the Kentucky Senator of "aligning himself with fundamentalist fanatics," and warned that the elder Paul's legacy would be "sullied by the son's untrammeled ambition."

On Wednesday, Raimondo fell in love. From his post on the filibuster (emphasis added):

I started writing this as Rand Paul entered the 9th hour of his historic filibuster against the nomination of John Brennan as CIA director, but I had to stop. As I listened and watched, real tears clouded my vision, raining down on the keyboard – tears of pure joy.

Quite an emotional reaction, and it took me by surprise: what, I wondered, is wrong with me? But perhaps my somewhat overwrought response wasn’t so inexplicable. After all, for years we’ve been subjected to a relentless assault on our civil liberties, with the War Party running roughshod over what weak dissents have surfaced – and now, finally, a clear voice of reason has emerged, to answer their war cries with a resounding "No!" Rand Paul, it turns out, truly is his father‘s son.

According to Paul aides and confidantes, the goal of his filibuster was always to introduce ideas about civil liberties back into the Republican discourse.

"Rand has always said that he wanted to be a leader on the message of the Republican Party, and that means talking about old ideas that were part of the party's original message, and introducing new ideas that might help the party broaden its appeal to groups that may have been left out of the conversation," Doug Stafford, Paul's Senate chief of staff, told Business Insider.

"Rand is one of the only people who can speak to libertarians, social conservatives, as well as your average mainstream Republican voter."

But no one, including Paul, anticipated the magnitude of support his filibuster would get, both from his Senate colleagues and from Republican activists on Twitter and Facebook.

"When have you ever seen a national debate about civil liberties? It never happens, but it happened Wednesday night and Rand got to lead that," Stafford said. "This kind of thing only happens when there is something that needs to be said, and it either isn't being said, or is being said in the wrong way."

Although Paul had planned to filibuster Brennan's confirmation for several weeks — and his staff had prepared several binders full of notes — the decision to do it Wednesday was spontaneous, and none of Paul's colleagues (with the exception of Mike Lee) were informed until Paul took the floor.

But the filibuster always had the tacit support of the Republican Senate leadership.

"Leader McConnell let it be known that he was cool with this, and that allowed some of this to take off," said Jesse Benton, a former Paul staffer who is now McConnell's campaign manager.

He added that McConnell ultimately decided to join Paul on the floor because "he was legitimately emotionally moved by it."

All this suggests that the assimilation of Establishment Republicans and Tea Party conservatives began long before their Wednesday night lovefest.

"I think we're seeing a great potential for synergy between leaders like McConnell...and then the new blood that is coming in with this new energy, and I think they are going to continue to work together," Benton said. "If there are Republicans that say they don't want to stand on principle, then I think they are going to find their role in the Republican Party shrinking."

*This post has been updated throughout.