The evidence so far

Our economy is strong, as nearly every new release of economic data indicates. Industrial production is up. The unemployment rate is as low as it has been in two decades. Employment rates are growing and the disability rolls are shrinking. Measures of business confidence are bullish. Stocks are up. The economy has been growing, hitting 3 percent in some quarters. Inflation, meanwhile, remains low.

Usually such good economic news redounds to the benefit of the political party in power. This rule probably applies today. Even though President Trump and Republicans are less popular than politicians presiding over robust economic expansions usually …