What a Secret Memo to Top Republicans Says About Donald Trump It was sent by the National Republican Senatorial Committee executive director.

 -- The head of the Republican committee charged with keeping the U.S. Senate under GOP control is actively preparing for the possibility of Donald Trump winning the GOP presidential nomination.

ABC News has learned that National Republican Senatorial Committee executive director Ward Baker wrote a secret memo to top staff in late September on how to run their campaigns if the real estate mogul is at the top of the ticket, describing the current GOP frontrunner as “a misguided missile” who is “subject to farcical fits” and advising its candidates to avoid getting tied too closely to Trump.

“We should prepare for 2016 by understanding the environment and recognizing the Trump phenomenon,” Baker writes in the confidential memo. “Understand the populist point Trump makes and ride that wave.”

The letter was first reported by the Washington Post.

Although Republicans currently hold a slim majority in the U.S. Senate, the party needs to hold several competitive seats in order to maintain their majority. The brash real estate mogul’s candidacy, once thought to be fleeting by top establishment Republicans but now entering its fifth month atop national polls, has sparked widespread worry about a potential wipeout effect on down-ticket races if he becomes a nominee.

“Let’s face facts,” the memo reads. “Trump says what’s on his mind and that’s a problem. Our candidates will have to spend full time defending him or condemning him if that continues. And that’s a place we never, ever want to be.”

The NRSC says that the group has written memos on every Democratic and Republican candidate. They shared the memo confidentially with trusted Republican advisors in September.

“It would be malpractice for the Senatorial committee not to prepare our candidates for every possible Republican and Democrat nominee and election scenario,” said NRSC spokeswoman Andrea Bozek.

A new Quinnipiac University poll today showed Donald Trump leading the Republican pack with 27 percent support, ahead of Ben Carson, Sen. Ted Cruz and Sen. Marco Rubio by double digits. And the memo clearly lays out the potential for Trump to win the nomination, offering specific advice on communications and how to focus a campaign on outsider reforms.

“If the environment aligns properly, Trump could win,” Baker wrote. “Spending full time attacking our own nominee will ensure that GOP vote is depressed. That will only serve to topple GOP candidates at every level. Maintain the right amount of independence, but avoid piling on the nominee.”

This news comes less than two weeks after Trump would not rule out mounting an independent bid for president if he isn’t “treated fairly.” His comment came even though he signed a pledge this summer that he would support the ultimate Republican nominee.

“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” in late November when asked about a new guerrilla effort by operatives within the Republican Party to derail Trump’s candidacy. “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."

The memo also warns candidates to distance themselves from Trump’s comments about women.

“Houston, we have a problem: Donald Trump has said some wacky things about women,” he wrote. “Candidates shouldn’t go near this ground other than to say that your wife or daughter is offended by what Trump said.”