That, more than the performance of any individual candidate, is the news out of the poll. That's how deep the disenchantment runs among Republican voters who believe their leaders have grossly over-promised and under-delivered. As I wrote last week, "the realization is sinking in that they are being played, that the base has been promised many many things that the party has no intent or capability of delivering."
It's also worth noting that the three establishment favorites have all dallied to varying degrees with compromise on the issue of illegal immigration. Bush continues to advocate what amounts to full if gradual legalization, and both Walker and Rubio have been forced to retreat from a similar position. As Trump reminded voters this weekend, Rubio had once been a co-sponsor of comprehensive immigration legislation in the Senate that the Donald called "nothing more than a giveaway to the corporate patrons who run both parties."
Trump made that comment in releasing his own policy proposals on immigration. In addition to building the border wall and making Mexico pay for it, he advocates deporting all illegal immigrants, including the so-called Dreamers brought here as young children. He wants to stop granting automatic citizenship to all those born on American soil, and he wants to temporarily halt the granting of additional green cards that allow legal immigrants to work here.
Give him credit: Trump knows what his target audience wants to hear, and he knows no shame in giving it to them. With those proposals, he is dragging the GOP even further to the right on immigration and making Bush even more exposed. Other candidates now have to choose whether to move right themselves or try to argue that Trump's proposals are too extreme, and that latter option would seem to conflict with the mood of the base.
UPDATE: Scott Walker appears to have made his choice.