Correction appended, March 2

In the final two weeks before Super Tuesday, Republican super PACs coalesced, airing roughly 8,500 ads blasting GOP front-runner Donald Trump, according to a Center for Public Integrity review of new data provided by Kantar Media/CMAG.

The ad blitz, however, may be too little, too late. Trump’s Republican rivals have been slow to attack him and only recently have singled him out on the airwaves.

“I don’t think [Republicans] saw him as a true threat,” said Travis Ridout, co-director of the Wesleyan Media Project, which tracks political advertising. “He breaks the mold of what we’ve seen in the past 50 years.”

Today’s GOP nominating contests in 12 states come after a three-state winning streak for Trump. Most recently, he captured 46 percent of the vote at the Nevada caucuses, heightening anxiety among the Republican establishment wing that once doubted his ascendance.

“People are starting to panic,” said Johanna Dunaway, a political science professor at Texas A&M University. “So now, you see the efforts to try to stop his path to nomination.”

Conservative Solutions PAC — a super PAC supporting Sen. Marco Rubio of Florida — waged a $4.5 million anti-Trump campaign in just the past week, according to federal campaign finance filings.

Ahead of Super Tuesday, Conservative Solutions PAC saturated the TV airwaves, launched digital ads and even turned to the mobile messaging application Snapchat.

At a rally in Georgia on Saturday, attendees could use a Snapchat “geofilter”— location-based images that overlay photos or video — to don a virtual red cap reminiscent of Trump’s signature “Make America Great Again” hat, which was instead emblazoned with the words “Stop the Con Artist.”

Conservative Solutions PAC reserved more than 4,500 ads spots that hounded Trump during the past week, according to Kantar Media/CMAG data. One ad titled “Know Nothing” slams Trump for not immediately disavowing the endorsement of David Duke, former leader of the Ku Klux Klan.

Katie Packer, a former Mitt Romney campaign staffer, established a super PAC solely dedicated to discrediting Trump. Formed days before the Feb. 1 Iowa caucuses, Our Principles PAC has spent about $4.4 million on anti-Trump ad barrages that cast him as a liberal.

For Super Tuesday, it aired anti-Trump spots nine times nationally, spending just over $400,000 on the ads.

Also targeting Trump is Club for Growth and American Future Fund — two conservative outside groups that have spent millions of dollars in recent elections.

Club for Growth aired nearly 1,000 ads ahead of Super Tuesday.

Meanwhile, American Future Fund — a group with ties to conservative billionaires Charles and David Koch — released three ads this week featuring former Trump University students who say they were scammed and forced into debt by Trump’s educational endeavor, which is now facing lawsuits in New York and California.

“I was trumped by Trump,” said one ex-Trump University student over a melancholy piano tune. “I was duped by the Donald.”

Republican Sen. Ted Cruz of Texas and Stand for Truth — a super PAC supporting Cruz — took jabs at Trump as well. Together they aired hundreds of ads critical of Trump.

The anti-Trump ads do not come without retaliation. Trump assailed Super Tuesday states in the South with more than 3,000 ads since Feb. 22.

So, will the last minute ad barrage work? Trump is predicted to sweep tonight’s Super Tuesday contests, and on Monday, he polled nationally better than ever.

“A sustained coordinated effort could definitely knock him down a notch or two,” said Ridout of the Wesleyan Media Project. “Is that enough for someone else to come in to prevent him from a nomination? Perhaps.”

Michael Beckel contributed to this report.

Correction: The original version of this story misstated the number of ads aired against Trump. In all, 8,500 were aired.

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