So much for “secular stagnation.” You remember that notion, made fashionable by economist Larry Summers and picked up by the press corps to explain why the U.S. economy couldn’t rise above the 2.2% doldrums of the Obama years. Well, with Friday’s report of 4.1% growth in the second quarter, the U.S. economy has now averaged 3.1% growth for the last six months and 2.8% for the last 12.

The lesson is that policies matter and so does the tone set by political leaders. For eight years Barack Obama told Americans that inequality...