Many are surprised that respected Republicans have fallen in behind him. They fear that if they do not, he will find a supporter in their state or district to take their party nomination at the next election, much as the tea party used to do.
It is hard to remember any precedent in American politics for a complete outsider taking over one of its major parties to this degree. Trump's dominance of the Republican Party appears absolute unless there is a John McCane among the new senators and House representatives or state governors elected yesterday.
The Senate, where only a third of the seats were up for election, has kept a Republican majority. Many outside America might have expected Republican senators to suffer for sending Judge Brett Kavanaugh to the Supreme Court only a few weeks ago.
It is a measure of how much American public opinion is out of step with the modern world, that Kavanaugh's appalling display in the televised hearing of a woman's complaint of sexual assault worked for Republicans in these elections.
Far from trying to bury the subject as soon as they could, Republicans campaigned on it, accusing Senate Democrats of injustice.
America has become a strange country under Trump. While he has lost control of the lower chamber of Congress, he has not done nearly as badly as his conduct in office deserved.
It is now over to the House Democrats to show that he no longer has things his own way but, more important, that Trump's style of politics is not theirs.
They need move the country past antagonism and division and do what they can to show the US dignified, respected and great again.