Is the GOP establishment trying to gang up on Trump?

Republican donors want to sink Donald Trump's nomination before, they fear, he sinks the party in 2016. And they're mounting an anti-Trump "guerrilla campaign" to unseat the outspoken billionaire's surprisingly resilient lead.

The campaign unites donors from a number of Republican rivals – potentially including Ohio Gov. John Kasich, former Fla. Gov. Jeb Bush, Texas Sen. Ted Cruz, and Fla. Sen. Marco Rubio – into one Trump take-down team.

Their goal, according to a memo reviewed by the Wall Street Journal, is to "defeat and destroy" the celebrity billionaire's candidacy.

The effort is led by a group called Trump Card LLC, run by Liz Mair, a former communications official for the Republican National Committee (RNC). It plans to run a series of anti-Trump TV, radio, and web ads and to pitch opposition research to local stations in early-voting states.

While some individual candidates have challenged Trump, thus far, there have been few efforts to boldly and collectively take on the surprise frontrunner, who has been leading almost every poll nearly since he declared his candidacy in June. Some have assumed that Trump, who has taken increasingly contentious stances, would fizzle out on his own. Others hoped to inherit his supporters when he faded.

But with the Iowa caucuses a little more than two months away and the real estate mogul still topping most polls, there appears to be a new sense of urgency in toppling Trump, says Frank Orlando, political science instructor at Saint Leo University in Saint Leo, Fla.

“People have been waiting for a Trump collapse for such a long time and now some are starting to panic. Everyone from public donors to public scientists have predicted his downfall, but now we're starting to reimagine the theories that the 'party decides.' Voting will be starting in Iowa before you know it and now people are starting to panic.”

It's a fear echoed by Ms. Mair.

“In the absence of our efforts, Trump is exceedingly unlikely to implode or be forced out of the race,” she wrote in the memo obtained by the Journal.

“The stark reality is that unless something dramatic and unconventional is done, Trump will be the Republican nominee and Hillary Clinton will become president."

And Mair's group isn't alone in the anti-Trump media blitz. A super PAC supporting Governor Kasich, New Day for America, plans to run a $2.5 million campaign against Trump, which donors for other candidates have also expressed interest in backing. On Thursday, ads began to air that portray Trump and retired neurosurgeon Ben Carson as ineffective and inexperienced leaders in the wake of the Nov. 13 Paris terrorist attacks. “On-the-job training for president does not work,” the ad says.

Trump reacted to the news in a multi-tweet barrage, including this posting:

The anti-Trump campaigns appear to be without precedent, as well as a breach of the party's "Eleventh Commandment," famously invoked by Ronald Reagan, which states that no Republican shall speak ill of a fellow Republican.

"Most of the candidates are usually acceptable in some way or another, and if they aren’t they usually are discovered and then fade away," says Professor Orlando. "What we haven’t seen before is the Republican establishment takedown of a candidate ..."

As such, they illustrate the party's rocky relationship with the outspoken surprise frontrunner, as well as its fear of how he might affect the race.

That fear, of course, is that Trump, whose views on immigration and minorities have become increasingly inflammatory, could win the nomination, handing the White House to Democrats in 2016.

Following the Paris attacks, Trump suggested closing down US mosques and requiring all Muslims in the United States to register in a special database. While his comments drew criticism from some rivals like Kasich and Governor Bush, it also led some observers to equate Trump's views with those of the Republican party.

In September, the RNC forced Trump to sign a petition pledging not to run as an independent. Now, Trump has indicated he may renege on that pledge if he's not treated fairly.

“I’m going to have to see what happens. I will see what happens. I have to be treated fairly,” Trump said Sunday on ABC’s “This Week." “When I did this, I said I have to be treated fairly. If I’m treated fairly, I’m fine. All I want to do is [have] a level playing field."