Trump’s support among Republican officeholders and party operatives may be thin, but he enjoys overwhelming support from Republican voters. The CNN poll I referenced shows a 90% approval rating among Republicans, and other polls show comparable numbers. That’s a strong incentive for Congressional Republicans to act like they support Trump, even if they personally don’t.

Of that 90%, many are Trumpian populists. They’re with him til the end. The others are mostly loyal partisans, who see a zero-sum game between Trump and liberals. It’ll take quite a bit for them to turn on a Republican president and help the Democrats.