By now, it's obvious to everyone with open eyes that Donald Trump is an ignorant, wildly dishonest, erratic, immature, bullying egomaniac. On the other hand, he's a terrible person. But despite some high-profile defections, most senior figures in the Republican Party -- very much including Paul Ryan, the Speaker of the House, and Mitch McConnell, the Senate majority leader -- are still supporting him, threats of violence and all. Why?
One answer is that these were never men and women of principle. I know that many in the media are still determined to portray Mr Ryan, in particular, as an honest man serious about policy, but his actual policy proposals have always been transparent con jobs.
Another answer is that in an era of intense partisanship, the greatest risk facing many Republican politicians isn't that of losing in the general election; it's that of losing to an extremist primary challenger. This makes them afraid to cross Mr Trump, whose ugliness channels the true feelings of the party's base.
Paul Krugman, a Nobel laureate in economics, is a political columnist with The New York Times.
But there's a third answer, which can be summarised in one number: 34.
What's that? It's the Congressional Budget Office's estimate of the average federal tax rate for the top 1% in 2013, the latest year available. And it's up from just 28.2 in 2008, because President Barack Obama allowed the high-end Bush tax cuts to expire and imposed new taxes to pay for a dramatic expansion of health coverage under the Affordable Care Act. Taxes on the really, really rich have gone up even more.
If Hillary Clinton wins, taxes on the elite will at minimum stay at this level and may even go up significantly if Democrats do well enough to enable her to pass new legislation. It's estimated her tax plan will raise the average tax rate for the top 1% by another 3.4 percentage points, and the rate for the top 0.1% by 5 points.
But if "populist" Donald Trump wins, taxes on the wealthy will go way down; in particular, Mr Trump is calling for elimination of the inheritance tax, which these days hits only a tiny number of really huge estates (a married couple doesn't pay any tax unless their estate is worth more than US$10.9 million).
So if you're wealthy, or you've built a career by reliably serving the interests of the wealthy, the choice is clear -- as long as you don't care too much about stuff like shunning racism, preserving democracy and freedom of religion, or for that matter avoiding nuclear war, Donald Trump is your guy.
And that's pretty much how the Republican establishment still sees it. Getting rid of the estate tax is "the linchpin of the conservative movement," one major donor told Bloomberg's Sahil Kapur. Gotta get those priorities straight.
Should we be shocked at the willingness of leading Republicans to make this bargain? Well, we should be -- we should never accept this sort of thing as normal politics. But we shouldn't be surprised, because it's just an extension of the devil's bargain the economic right has been making for decades.
Don't take my word for it; listen to the conservatives who have reached their limit. Recently Avik Roy, a leading Republican health-policy expert, had the personal and moral courage to admit what liberals (and political scientists) have been saying for years: "In reality, the gravitational centre of the Republican Party is white nationalism."
Just to be clear, I'm not saying that top Republicans were or are personally bigoted -- but that doesn't matter.
What does matter is that they were willing to curry favour with bigots in the service of tax cuts for the rich and financial deregulation. All that has happened this year is a move of those white nationalists from part of the supporting cast to a starring role.
So when Republicans who went along with the earlier strategy draw the line at Trump, they're not really taking a stand on principle; they're just complaining about the price.
If this election goes the way it probably will, a few months from now those leading Republicans will be trying to pretend that they never really supported their party's nominee, that in their hearts they always knew he was the wrong man.
But whatever doubts they may be feeling doesn't excuse their actions, and in fact it makes them even less forgivable. For the fact is that right now, when it matters, they have decided that lower tax rates on the rich are sufficient payment for betraying American ideals and putting the republic as we know it in danger.