The failure of anyone to attack Trump over the airwaves is irrational and not in the GOP’s best interests as a party, since he would clearly be a catastrophically bad general election candidate, and while I don’t believe he’ll be the nominee, you can’t make that happen without trying. We have vast amounts of evidence from past campaign seasons that negative ads work, and no rational basis for believing that they would have no effect on at least dampening Trump’s ability to add new supporters. The one sustained campaign run against Trump earlier in this campaign, by the Club for Growth in Iowa, coincided with the first time Trump lost a lead in the polls anywhere. There may be debate over what the best angle of attack would be, mostly because Trump presents such a wealth of targets, but that’s why you test out a few options and run with what makes the biggest dent. This is not rocket science, it’s how campaigns have been run since time immemorial, in general elections and in both sides’ primaries.
I realize we’re at the peak of the season for everybody and his uncle trying to claim the mantle of the guy “the establishment” hates – as if the GOP establishment was a monolith rather than a loose confederation that couldn’t organize a potluck supper, much less a political campaign (lest we forget, we got to this point in large part because people lost faith that the party establishment was even competent at doing the things we expect party establishments to do). But if you want to know which candidate everybody else in the race truly fears, which candidate people are willing to invest donor money in attacking, follow the money. It’s not Trump. It’s not Cruz. It’s Rubio.