Sens. Rand Paul (R-Ky.), left, and Mitch McConnell (R-Ky.) before a White House event on July 23, 2013. (Brendan Smialowski/AFP/Getty Images)

Mitch McConnell stood at his desk on the Senate floor after 1 a.m. Saturday, the eyes of his colleagues trained on him. He seemed bewildered.

“Enter your motion to reconsider,” Laura Dove, his chief floor aide, told the majority leader, the exchange audible throughout the chamber. “You need to enter your motion to reconsider.”

McConnell has studied Senate procedure firsthand over five decades, and there is not much that can leave him flummoxed, even momentarily. But here he stood — thanks to, of all people, his fellow Republican, fellow Kentuckian, close political ally and the man he has endorsed for president — Sen. Rand Paul.

With a dramatic series of procedural maneuvers, Paul had just dashed McConnell’s public pledge to extend a controversial National Security Agency surveillance program beyond a June 1 deadline before the Senate left for a week-long holiday break. The program allows the government agency to collect vast troves of call data from telephone companies as part of the fight against international terrorism. Paul sees it as a violation of individual privacy.

Sen. Rand Paul (R-Ky.) took to the floor Wednesday afternoon to "filibuster" the renewal of the Patriot Act. Paul claims it gives government too much access to citizens’ private cell phone records. (C-SPAN)

“Our forefathers would be aghast” at the spying, Paul declared in front of McConnell, who once favorably compared Paul to Kentucky statesman Henry Clay.

Moments later, McConnell announced that the Senate would return a day early for a rare Sunday session May 31, giving him just a few hours of business to prevent a scenario that he had repeatedly warned would pose a grave threat to national security.

“My colleagues, do we really want this law to expire?” he asked. “We’ve got a week to discuss it; we’ll have one day to do it.”

The early-morning antics not only complicated senators’ vacations but created a new chapter in the evolving relationship of McConnell and Paul, who have come to symbolize the once-tenuous but now increasingly comfortable ties between tea party conservatism and the Republican Party mainstream.

McConnell, the consummate insider, and Paul, the populist firebrand, have become increasingly close since Paul crushed McConnell’s hand-picked Senate candidate in the 2010 Republican primary — culminating with Paul campaigning strenuously last year for McConnell’s sixth Senate term, and McConnell returning the favor this year with an endorsement of Paul’s presidential bid.

“We’ve developed a very tight relationship, and I’m for him,” McConnell told the Lexington Herald-Leader last year.

Their paths have now diverged. Paul is seeking to motivate his activist base with a mantra of “defeat the Washington machine” as he tries to distinguish himself in a crowded GOP presidential field, while McConnell is trying to corral his fellow Republican senators to govern effectively to boost the party’s standing ahead of the 2016 elections.

Paul played down any tensions with his senior colleague. “I think we have good relations,” he said last week. “Really, period. We’re friends and we disagree on this issue. . . . We have disagreements in our caucus all the time. But I try to keep it on a friendly basis, and, you know, I don’t think this will hurt our friendship.”

Don Stewart, a spokesman for McConnell, said: “They’re friends and work together well for Kentucky. They have different opinions on the Patriot Act.”

The first signs that Paul’s presidential ambitions and McConnell’s desire for smooth governing might be at cross purposes came Wednesday, when Paul held the Senate floor for nearly 11 hours to decry any extension of the current surveillance law at a time when senators were working through complex trade legislation that McConnell promised to pass by week’s end.

Paul said he did not warn McConnell before starting what he deemed a filibuster, but McConnell aides played down the speech, saying it did not delay consideration of the trade bill, which passed a final vote Friday evening.

But Paul’s maneuvering afterward most certainly went against McConnell’s wishes. With Paul leading the objections to a short-term extension of the existing legal authority for the NSA program, it highlighted McConnell’s tactical missteps in delaying consideration of the surveillance program and undermined any attempt he might have made to blame its potential expiration on Democrats.

Instead, the Democrats were gleefully blaming McConnell for the impasse.

“This mess is an entirely predictable consequence of Senator McConnell’s bad habit of governing by manufactured crisis,” said Adam Jentleson, a spokesman for Senate Minority Leader Harry M. Reid (D-Nev.). “Senator McConnell badly misjudged the members of his own conference and failed to listen to advice from Senator Reid and others who saw this mess coming weeks ago and tried to warn him.”

There are other signs that relations between McConnell and Paul have become strained. According to Democratic aides, Reid approached McConnell late Friday night to ask about the possibility of moving up consideration of surveillance legislation by an hour — something that would require Paul’s consent.

But McConnell refused to ask Paul to accelerate the vote, the aides said, so Reid asked a Democratic ally of Paul’s on surveillance reform, Sen. Ron Wyden of Oregon, to approach him and ask for the accommodation. (Stewart said that McConnell did not refuse and that it was Republican floor staff, not Wyden, who secured Paul’s consent to move up the votes.)

Attitudes toward Paul — especially those of fellow Republicans — sharpened as the long night wore on. A camera captured Sen. Lindsey O. Graham (R-S.C.) rolling his eyes at Paul’s floor remarks, while Sen. Claire McCaskill (D-Mo.) tweeted her exasperation, accusing Paul of “using Senate rules to grandstand.”

“Frustrating for those of us who actually want to reform NSA,” she said.

Many had hoped that Paul’s marathon floor speech Wednesday — or “performance,” as Sen. John McCain (R-Ariz.) called it — would suffice to make his point.

It did not. Paul objected to a seven-day extension to the current law, taking advantage of Senate rules protecting the right of an individual senator to oppose quick action on any question. McConnell then proposed, in turn, four-day and two-day extensions, which were opposed by Wyden and Martin Heinrich (D-N.M.), respectively.

When McConnell finally offered a one-day extension, Paul objected again, prompting the unusual Sunday session.

“There’s a new breed in the Senate, and we have seen the manifestation of it,” McCain said afterward. “One or two or three are willing to stand up against the will of the majority. Some time ago, the Senate people would sit down and try to work things out. And obviously these individuals don’t believe in that. But I’m sure it’s a great revenue-raiser.”

Throughout recent days, Paul’s presidential campaign issued a steady stream of e-mail solicitations to supporters and a flurry of tweets to the world highlighting his efforts to end the NSA surveillance program.

“My filibuster will continue, but I need some extra muscle from the grass roots to keep it going,” one missive read. “I hope you’ll please stand with me by chipping in a generous contribution. I could use your help right now like never before.”

Asked about those dismissing his surveillance stand as a fundraising ploy as he left the Capitol early Saturday, Paul said, “I think people don’t question my sincerity.”

It is unclear what difference a week will make in the surveillance debate. The positions of national security hawks such as McConnell and civil libertarians like Paul have barely softened, while a House-passed, White House-supported compromise measure — the only legislation offering a seamless transition — was unable to gain the 60 votes necessary to proceed. A procedural vote on the bill failed 57 to 42.

“Sometimes things change as deadlines approach,” Paul said.

Paul Kane, Ellen Nakashima and Katie Zezima contributed to this report.