Updated 12:34 p.m. | Sen. Rand Paul is calling the debate on an issue that puts him at odds with Majority Leader Mitch McConnell "a defining moment for our country."
In a series of tweets, the junior Kentucky Republican declared he would do what was in his power to preclude reauthorization of expiring National Security Agency surveillance powers under the Patriot Act.
"I will fight tooth-and-nail to stop a blanket reauthorization of this attack on our freedoms," Paul said on Twitter. "But the defenders of the surveillance state are going to do everything they can to defeat you and me."
A petition posted on his presidential campaign website seeking signatures to support a statement says, in part: "Today, our Fourth Amendment which protects Americans from government search and seizure unless there is probable cause of a crime is under assault like never before."
The petition concludes: "Therefore: I will stand with Senator Paul in as he makes ending the NSA's illegal domestic spying on day one in the Oval Office a centerpiece of his campaign."
The tweets refer to a more immediate test than what Paul would do after taking the oath of office as president: the debate on Capitol Hill over extending provisions under Section 215.
The fight has been brewing for months, even before Thursday's court decision ruling the bulk phone collection program illegal .
McConnell, Paul's senior Kentucky colleague, has formally backed Paul's presidential bid, though surveillance is one area where the two senators don't agree.
McConnell said Tuesday the base bill for a Senate debate on extending the authorities past the end of the month would be a "simple extension," rather than the kind of overhaul bill that's expected to appear on the House floor as early as next week after moving through the House Judiciary Committee.
McConnell has introduced a five-and-a-half year clean extension along with Intelligence Chairman Richard M. Burr, R-N.C.
"I think, most likely, the outcome is some kind of extension. Chairman Burr and I consulted and we agree that the underlying bill would be a simple extension. But it will be open for amendment, whenever we're able to really full turn to it. The question is whether we can do all that between now and Memorial Day," McConnell said. "And I can't tell you right now."
Senate Democrats are already expressing concern that McConnell might attempt to "jam" through an extension with the deadline (and perhaps more significantly to some senators, a state work period) looming.
While the duration of the extension that Republican leadership would seek to advance is a question, there's no doubt the approach heading into an amendment debate would be decidedly different than what Sens. Mike Lee, R-Utah, and Patrick J. Leahy, D-Vt., have introduced to constrain NSA operations.
That bill, the USA Freedom Act, would "neither keep us safe nor protect our privacy," McConnell said Thursday.
Paul drew the ire of some civil liberties supporters for going against the legislative overhaul effort led last year by Leahy when the Vermonter chaired the Judiciary Committee. A pitch to limit debate late in 2014 fell two votes short of the 60 needed to overcome the filibuster threat. Paul indicated at the time that he did not view the overhaul as going far enough.
With the deadline approaching, the question now is what, if anything can pass both the House and the Senate that would be amenable to the White House. Allowing the programs to lapse would be a win for Paul's side of the debate.
"Our movement is the biggest threat to the Washington Machine's grip on power," Paul said on Twitter. "Nowhere is that more clear than the fight over the so-called 'PATRIOT Act's' warrantless spying provisions."
But the leader of that "Washington Machine" on this particular issue might prove to be McConnell, rather than President Barack Obama.
Related: Appeals Court Strikes Down NSA Bulk Phone Data Collection The 114th: CQ Roll Call's Guide to the New Congress Get breaking news alerts and more from Roll Call in your inbox or on your iPhone.