This has been a week for severing ties with Donald Trump. NBC cut him loose over the comments he made about Mexican migrants in his presidential announcement. Trump claims he's voluntarily parting ways with Macy's.

One group that seems to be sticking with Trump is the Republican primary electorate. This week the real estate mogul has finished second in a national poll, second in New Hampshire and tied for second in Iowa. With the exception of the first-in-the-nation caucuses, the candidate who gets the top spot when Trump comes in second is Jeb Bush.

That's partly because Trump's surge seems to have come at the expense of other more viable conservatives. The CNN/ORC poll that has Trump taking 12 percent of the GOP vote nationally has Scott Walker knocked back to 6 percent, behind Mike Huckabee, Ben Carson and Rand Paul (who are themselves in single digits) and alongside Marco Rubio.

Early polls don't mean much — remember the 2011 leads enjoyed by Herman Cain and Michele Bachmann? — and to the extent they do, Walker's team would certainly prefer to lead in Iowa than in some national survey. But with so many candidates running and bunched in together, Trump's strength is preventing the conservative primary-within-a-primary from sorting in the same way that Bush has clearly become the establishment favorite over Chris Christie.

It's easier to see Bush winning a Mitt Romney-style war of attrition against Trump for the GOP nomination too. With Walker, Rubio or Paul, conservatives might not face such a dilemma between their hearts and their heads. They can vote for the candidate they think is more conservative without getting laughed out of the room in the general election.

If it's Trump vs. Bush, not only are there serious questions about the brash reality TV star's conservatism, there would be an electability gap the former Florida governor could exploit to win the nomination. And if a strong stance against illegal immigration is what's fueling Trump's momentum, it would be ironic, to say the least, for Bush to be the beneficiary

Perhaps Trump's rise is primarily attributable to name ID and media attention, especially since most of the field can't consistently break into double digits. But some conservative prioritize combativeness and irritating liberals over policy accomplishments or political philosophy. They could be tossing aside the best chance they've had since 1980 to turn to the Republican establishment and say, "You're fired."