Trump presents a dilemma, or perceived dilemma, for other Republican candidates. He can't be ignored. You can't wait for him to self-destruct. I mean, when a candidate is already that brazenly atrocious, what is there to self-destruct? But if you attack him, must you sink to his own level?
I don't think Trump's opponents should resort to dirty tricks. They need to be honest. And with Trump, there's such a wealth of tawdry material.
Likewise, I don't think Trump's opponents should substitute ad hominem for substance. Candidates need to discuss substantive issues. But in addition to that, Trump makes it necessary to go negative, to go ad hominem.
This isn't a question of lowering yourself to his level, but simply getting off a patrician pedestal. One reason Jeb lost is that he had a courtly code of honor.
But this is not a gentleman's game. And that's an artificial standard to begin with. A rather effete, highbred affectation.
The stakes are far too high in this election to worry about your dignity. This is not a Jane Austen novel.
You can't play football by badminton rules, or ice hockey by croquette rules. That isn't stooping to win–but just adapting to the nature of the game.
To be unrefined is not a moral vice. Don't confuse ethics with etiquette. If that's what it takes to beat Trump–or Hillary, for that matter–go for it.