Government spying has been one of Rand Paul's signature issues on the presidential campaign trail. And as the U.S. Congress spirals closer toward an expiration of key sections of the Patriot Act, Paul is revving up his messaging in hopes grassroots donors are ready for the show.

In a literally explosive ad released Friday, America's Liberty PAC, a super PAC established to back Paul that has been sanctioned by the senator, sounded the alarm that "Sunday, Sunday, Sunday" would be a showdown worth tuning in for.

After failing to negotiate a deal to temporarily extend or even reboot key national-intelligence programs, including the collection of bulk metadata, a week ago, Majority Leader Mitch McConnell summoned senators to return this Sunday—one day before the programs expire completely.

If the fiery ad is any indication, Paul isn't going to let the program be renewed without a fight.

The ad calls Sunday's session "the biggest brawl for liberty of the century," as a bald eagle soars across the screen spitting fire. It then goes on to present Paul and President Obama as bobble heads on a collision course, depicting them as "the biggest rivals" (although the White House has said it supports an overhaul of the intelligence gathering programs, just not one Paul supports).

As an enhanced image of a shirtless and sunglasses-clad Paul emerges in flames, the narrator describes Paul as the "defender of Freedom" and Obama as "the head of the Washington spy machine." But the PAC doesn't stop short of calling out the president's "conservative accomplices," including "the capitulating Canadian" Sen. Ted Cruz, a fellow 2016 presidential contender who has backed the USA Freedom Act, considered a reform bill, which would end the government's collection of bulk data and only allow it to access phone records they need from telecom companies on a case-by-case basis. Paul has said that bill does not go far enough. Cruz, though, did join Paul on the Senate floor last week at the close of his self-declared "filibuster" against the National Security Agency program.

America's Liberty PAC also ambushes Sen. Lindsey Graham in the ad, who supports the intelligence-gathering programs that are set to expire Monday and is also considering a presidential run.

"Kids we haven't forgotten about you," the narrator says as the screen switches to kids playing with a plastic car that has computer-generated flames under its wheels. "Senator Lindsey Graham tries to read your emails while doing doughnuts in a pink 1997 Geo Metro."

Absent from the ad, however, was any mention of Sen. Marco Rubio, another presidential competitor and a fierce defender of bulk-data collection and other security programs set to expire.

For Paul, the NSA programs have been a key part of his candidacy. Last week, Paul fundraised off of his self-proclaimed filibuster, with his campaign selling "filibuster starter packs" during his 10-and-a-half-hour speech.

The super PAC ad comes just as the financial viability of Paul's presidential campaign has come into question. As Politico noted Friday, in a campaign where big donors are often able to give unlikely candidates a leg up on their competition, Paul has failed to garner big-name support. Instead, he continues to rely on smaller donors. Despite appeals to big names like Peter Thiel, Napster co-founder Sean Parker, or even big donors in his own home state of Kentucky, Paul has found himself to be the same kind of libertarian-leaning rogue candidate his father was known as.

And in those situations, an off-beat political ad may be the best chance of dredging up grassroots support.

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