The other paradox of the Trump Presidency is his low approval rating despite a stronger economy. The polls show his approval rating on the economy is above 50% but his overall approval is 44.3% in the Real Clear Politics average. The difference is best explained by Mr. Trump’s polarizing behavior, which has alienated in particular college-educated voters and Republican women. In the latest Wall Street Journal-NBC poll, Mr. Trump is underwater with white college-educated women by a remarkable 20 percentage points.

Mr. Trump may figure he can persuade some of those skeptics by making the Democratic nominee even more unpopular than he is. If the Democrats oblige by nominating Bernie Sanders or Elizabeth Warren, that might be possible. But that is making a bet on the other party’s mistake, and a re-election campaign is typically a referendum on the incumbent.

Which is all the more reason to offer voters something more for a second term. He could put Democrats on the spot for high housing prices and homelessness by talking about restrictive zoning for elites and high property taxes. He could offer to reform higher education by making schools responsible for some of the debt of students who can’t repay loans, or invigorate vocational education to help young people who can’t go to college.