It turns out that the millionaire GOP establishment donor who bankrolled the anti-Donald Trump skywriting at the Rose Bowl parade on New Year’s Day isn’t just any ordinary donor-class millionaire. He’s backing Sen. Marco Rubio (R-FL), the man who is emerging as the anti-conservative establishment and donor-class candidate for president in 2016.

According to the Center for Responsive Politics, Luther Stan Pate IV—an Alabama real estate developer worth millions—has donated thousands of dollars to Rubio’s electoral efforts.

On Jan. 29, 2015, Pate donated $5,200 to Rubio—who, at the time, hadn’t yet officially launched a presidential campaign but was acting as if he were running for president.

Just days earlier, ABC News’ Jonathan Karl reported exclusively that Rubio had hired Anna Rogers, then the finance director for Karl Rove’s American Crossroads, to lead “the effort to raise the $50 million or more he’ll need to run in the Republican primaries.”

“He has told us to proceed as if he is running for president,” a senior Rubio adviser told ABC News for the piece, which ran on Jan. 23, 2015—six days before Pate’s donation to Rubio.

A couple months later, Pate gave another $2,500 to Rubio, according to the Center for Responsible Politics. Later in the year, after Rubio launched his presidential campaign, the Rubio campaign returned $5,000 of the $7,700 total that Pate had donated to him. That is standard operating procedure because the Federal Election Commission (FEC) only allows donors to make a total of $2,700 to an individual presidential candidate.

Pate is the man who set up, on Dec. 29, a new anti-Trump Political Action Committee. FEC filings show that Pate is listed as the Treasurer and Custodian of Records for the new group entitled the “WeThePeople Foundation.”

That organization wrote messages like “America is great. Trump is disgusting” and “Anybody but Trump” and “Iowans dump Trump” in the sky at the Rose Bowl with at least five skywriting planes on Friday. Skywriting is a fairly expensive endeavor, and doing so with five planes makes it even more expensive.

The skywriting also directed viewers to the Rubio campaign-donor Pate’s new PAC website, http://anybodybuttrump.us/, a crudely designed site that viscerally attacks the 2016 GOP frontrunner.

The website allows visitors to donate to the Rubio campaign-donor Pate’s new PAC, to buy anti-Trump items from the organization’s online store, and to display various videos and anti-Trump materials.

Pate is an eccentric establishment GOP figure who’s been associated with behavior similar to this before.

Lagniappe, a weekly newspaper in Mobile, Alabama—Pate is based in Tuscaloosa—devoted an August 2007 cover story to Pate’s sharp-elbowed political tactics.

“In mid-2005, Pate sought $16 million in public funds for a real estate development, a shopping center to be named Midtown. The Tuscaloosa City Council declined [to grant] the aid with Council President Jerry Plott and Councilman Kip Tyner being the most vocal opponents,” said the article, which was also picked up by various local bloggers.

It wasn’t Pate’s first difficulty with the councilmen and he was frustrated. “He [Pate] fought us tooth-and-nail to get that money,” Plott said. “But I didn’t think public dollars should be spent on a private business. He began a public crusade to try to destroy me.” Pate apparently conceived a Web site aimed at fomenting discord against Plott. Amidst the many charges of corruption on www.theplottthickens.com, a dormant discussion board asks for feedback on the councilman and a line on the site declares, “I am Stan Pate and I approve this message,” then gives a Northport post office box address. Pate admits to having founded the site and claims good reason for such. “I filed an ethics complaint that is a matter of public record against Mr. Plott,” Pate said, “and I made it very clear in multiple ads and in the newspaper and in Tuscaloosa and on various publications that I feel like Mr. Plott’s dealings while he was on the city council were unethical and corrupt.”

At this time, Rubio’s team is not disavowing the efforts his donor Pate has taken against Trump. Alex Conant, Rubio’s communications director, has not responded to a request for comment when presented with evidence that the Rubio campaign’s donors are behind this attack on Trump.

While Trump has battled with pretty much everyone in the entire GOP field in 2016, he’s crushed a few candidates: former Florida Gov. Jeb Bush, Ohio Gov. John Kasich and Sen. Rand Paul (R-KY) are among those still running. And outgoing Louisiana Gov. Bobby Jindal, former Texas Gov. Rick Perry, Sen. Lindsey Graham (R-SC), former New York Gov. George Pataki and Wisconsin Gov. Scott Walker are among those not running anymore.

But there are a few candidates that Trump is treating carefully.

Rubio is one of them. Trump has been very critical of Rubio’s pro-amnesty positions on immigration, his work on trade, and Rubio’s horrendous attendance record when it comes to votes and national security briefings in the U.S. Senate. But he hasn’t gone as aggressively after Rubio as he has gone after, say, Bush.

Rubio is the last remaining establishment-backed candidate who’s got a clear shot at the nomination.

Bush and Kasich and New Jersey Gov. Chris Christie all could bounce back, but each of them is struggling and Rubio is the only non-conservative in the top-tier of polling along with Trump, Sen. Ted Cruz (R-TX) and Dr. Ben Carson.

That means Rubio presents basically the only threat to conservatives’ chances in 2016—and now that Rubio’s team is coming after Trump this aggressively, with the skywriting above the Rose Bowl in Pasadena, Rubio may have just inadvertently wandered into the bear’s den.