President Trump might not have won the Nov. 8 election had he not published a list of conservative judges from which he promised to pick his nominee to the Supreme Court.

There is no sign that the president, who will make his nomination Tuesday evening, is having second thoughts. But if, for the sake of showmanship or anything else, he is tempted to make a surprise pick, he should suppress that feeling at all costs. The list is a talisman among conservative and Republican voters, and a test of the value of the president’s word and his ideological seriousness. If he does not pick from the list it will cost him a permanent loss of support and gain him the enmity of people he needs over the next four years.