The establishment wing of the Republican Party has coalesced around the idea that Donald Trump must be stopped. Now it's just a matter of whom they deem worthy of carrying out the honors.

With Trump's lead among fellow Republican candidates in several national and state polls surprisingly holding firm, CNN reports party leaders are now debating how best to take direct aim at the bombastic real estate mogul.

CNN's Maeve Reston reports most GOP strategists see huge risks in having other candidates, or even the super PACs (political action committees) directly linked to them, carry out the attacks.  

"There are a lot of donors out there who see it as much too dangerous, obviously, for the candidates, or their allied super PACs, to go after Trump," said Reston. "So they're looking to more establishment PACs to potentially take him down in post-Labor Day ads."

Count former Republican presidential nominee Mitt Romney as among those within the party who are not necessarily big fans of Trump. To date Romney has resisted all efforts to recruit him into the race for yet another run.  

"He's very surprised that Jeb Bush hasn't got a lot of traction," Washington Post political writer Robert Costa told CNN. "He thought Jeb would be better at this point. He also thinks the race doesn't really start until January and February."

Word is Romney is not planning to run, no matter what, but aims to keep close watch as the race further unfolds.

"He thinks the race begins in January and February, and he's watching it very closely, and people just kept telling me the same thing," said a source.

One issue on which Trump has particularly sparked much reaction is the subject of immigration and his call for mass deportations. On Sunday, Bush took aim at those policies.

"He wants everyone deported, which would tear family lives asunder," Bush told New York radio talk show host John Catsimatidis. He later deemed Trump's plans "unconstitutional."