And here’s what’s interesting: all indications are that Mr. Bush’s attacks on Mr. Trump are falling flat, because the Republican base doesn’t actually share the Republican establishment’s economic delusions.

The thing is, we didn’t really know that until Mr. Trump came along. The influence of big-money donors meant that nobody could make a serious play for the G.O.P. nomination without pledging allegiance to supply-side doctrine, and this allowed the establishment to imagine that ordinary voters shared its antipopulist creed. Indeed, Mr. Bush’s hapless attempt at a takedown suggests that his political team still doesn’t get it, and thinks that pointing out The Donald’s heresies will be enough to doom his campaign.

But Mr. Trump, who is self-financing, didn’t need to genuflect to the big money, and it turns out that the base doesn’t mind his heresies. This is a real revelation, which may have a lasting impact on our politics.

Again, I’m not making a case for Mr. Trump. There are lots of other politicians out there who also refuse to buy into right-wing economic nonsense, but who do so without proposing to scour the countryside in search of immigrants to deport, or to rip up our international economic agreements and start a trade war. The point, however, is that none of these reasonable politicians is seeking the Republican presidential nomination.