Donald Trump has just had an extraordinarily bad week, and Hillary Clinton an extraordinarily good one; betting markets now put Mrs. Clinton’s odds of winning almost as high as they were just after the Democratic convention. But both Mrs. Clinton’s virtues and Mr. Trump’s vices have been obvious all along. How, then, did the race manage to get so close on the eve of the debate?A lot of the answer, I’ve argued, lies in the behavior of the news media, which spent the month before the first debate jeering at Mrs. Clinton, portraying minor missteps as major sins and inventing fake scandals out of thin air. But let us not let everyone else off the hook. Mr. Trump couldn’t have gotten as far as he has without the support, active or de facto, of many people who understand perfectly well what he is and what his election would mean, but have chosen not to take a stand.

Let’s start with the Republican political establishment, which is supporting Mr. Trump just as if he were a normal presidential nominee.

I’ve had a lot of critical things to say about Mitch McConnell, the Senate majority leader, and Paul Ryan, the speaker of the House. One thing of which I would never accuse them, however, is stupidity. They know what kind of man they’re dealing with — but they are spending this election pretending that we’re having a serious discussion about policy, that a vote for Mr. Trump is simply a vote for lower marginal tax rates. And they should not be allowed to flush the fact of their Trump support down the memory hole when the election is behind us.

This goes in particular for Mr. Ryan, who has received extraordinarily favorable press treatment over the years — portrayed as an honest, serious policy wonk with a sincere concern for fiscal probity. This reputation was never deserved; his policy proposals have always been obvious flimflam. But in the past, criticisms of Mr. Ryan depended on pointing out hard stuff, like the fact that his numbers didn’t add up. Now it can be made much simpler: Every time he’s held up as an example of seriousness, remember that when it mattered, he backed Donald Trump.

While almost all Republican officeholders have endorsed Mr. Trump, the same isn’t true of what we might call the G.O.P. intelligentsia – actual or at least self-proclaimed policy experts, opinion writers, and so on. For the most part, the members of this group haven’t spoken up in support of this year’s Republican nominee. For example, not a single former member of the Council of Economic Advisers has endorsed Mr. Trump. If you look at who has endorsed Mr. Trump — say, at the signatories of the statement of support from “Scholars and Writers for America” — it’s actually a fairly pathetic group.

But if you think that electing Mr. Trump would be a disaster, shouldn’t you be urging your fellow Americans to vote for his opponent, even if you don’t like her? After all, not voting for Mrs. Clinton — whether you don’t vote at all, or make a purely symbolic vote for a third-party candidate — is, in effect, giving half a vote to Mr. Trump.

To be fair, quite a few conservative intellectuals have accepted that logic, especially among foreign-policy types; you have to give people like, say, Paul Wolfowitz some credit for political courage. But there have also been many who balked at doing the right thing; when Henry Kissinger and George Schultz piously declared that they were not going to endorse anyone, it was a profile in cowardice.

And the response from sane Republican economists has been especially disappointing. Only charlatans and cranks have endorsed Mr. Trump, but only a handful have risen to the occasion and been willing to say that if keeping him out of the White House is important, you need to vote for Mrs. Clinton.

Finally, it’s dismaying to see the fecklessness of those on the left supporting third-party candidates. A few seem to believe in the old doctrine of social fascism — better to see the center-left defeated by the hard right, because that sets the stage for a true progressive revolution. That worked out wonderfully in 1930s Germany.

But for most it seems to be about politics as personal expression: they dislike Mrs. Clinton — partly because they’ve bought into a misleading media image — and plan to express that dislike by staying at home or voting for someone like Gary Johnson, the Libertarian candidate. If polls are to be believed, something like a third of young voters intend to, in effect, opt out of this election. If they do, Mr. Trump might yet win.

In fact, the biggest danger from Mr. Trump’s terrible week is that it might encourage complacency and self-indulgence among voters who really, really wouldn’t want to see him in the White House. So remember: Your vote only counts if you cast it in a meaningful way.

<Trump’s Fellow Travelers>