So, whatever Trump’s true ideological predilections, there’s no place for him to go. Make deals with the Democrats? At this point, Democrats are more likely to cooperate with Sergey Kislyak on an infrastructure package than with Trump. Perhaps reflecting this state of play, Trump’s infrastructure ideas have been moving steadily rightward.

Dump or triangulate away from Republicans? Well, then who would do scandal defense, aside from a handful of White House aides and outside media loyalists? Imagine what the Comey or Sessions hearings would have looked like if Republicans had joined Democrats in piling on.

The need for support on Capitol Hill could well grow more urgent if things go badly during the next year and a half. If Democrats take the House, Trump will rely on Republicans for an impeachment defense and, if it comes to that, for the votes in the Senate to block removal.