National Economic Council Director Gary Cohn (L) and US Secretary of the Treasury Steven Mnuchin take questions on tax cuts and reform during a briefing at the White House April 26, 2017 in Washington, DC.

The Republican-party establishment is caught in an existential paradox. Without Donald Trump's populist and nationalist 2016 campaign, the GOP probably would not have won the presidency.

Nor would Republicans now enjoy such lopsided control of state legislatures and governorships, as well as majorities in the House and Senate, and likely control of the Supreme Court for a generation.