Normally smart people, like Mitt Romney, discarded all their best instincts to suck up to this ragtag assortment of self-appointed G.O.P. commissars, each representing a different slice of what came to be Republican orthodoxy — climate change is a hoax; abortion, even in the case of rape or incest, is impermissible; even common-sense gun laws must be opposed, no matter how many kids get murdered; taxes must always be cut and safety nets shrunk, no matter what the economic context; Obamacare must be destroyed, even though it was based on a Republican idea; and Iraq was a success even though it was a mess.

The G.O.P. became an accretion of ideas that ossified over the years without the party ever stopping to ask afresh: What world are we living in now? What are the dominant trends? And how does America best exploit them by applying conservative values and market-based solutions?

The cynicism of today’s G.O.P. could not have been more vividly displayed than when Marco Rubio, John Kasich (a decent guy) and Ted Cruz all declared that they would support the party’s nominee, even if it was Trump, right after telling voters he was a con man. No wonder so many Republicans are voting for Trump on the basis of what they think is in his guts. All the other G.O.P. candidates have none.

But even if his support is weakening, Democrats take Trump lightly at their peril. He is still sitting with three aces that he hasn’t played yet. They could all come out in the general election.

One ace is that if he wins the nomination he will have no problem moving to the center to appeal to independents and minorities. He will have no problem playing the moderate unifier — and plenty of people will buy it, saying: “Why not give him a chance? He says he can make us winners.” Sure, Mexico will have to pay for that wall, Trump will say, but it will be in “installments.” Deport 11 million illegal immigrants? C’mon, don’t you know an opening bid on an immigration bill when you hear one? Ban all Muslims? Well of course we can’t ban a whole faith community, but Trump will vow to be much harder on visas from certain countries. Have you never read “The Art of the Deal”?