For the libertarian wing of the party, Paul's filibuster — and the groundswell of support for it across the conservative movement — was a crowning moment for their reintegration into the mainstream of the GOP, 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.

"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, by the end of it, you had people like Marco Rubio and Saxby Chambliss joining in.