Primary season for this year's midterm election is now nearly closed, and the results have produced an outcome not seen in years: Incumbent Republican senators have brushed back all their conservative challengers in a series of victories for the party's embattled establishment.
The results, capped by wins this week by Republican Sens. Lamar Alexander in Tennessee and Pat Roberts in Kansas, seem to run counter to Americans' sour mood about Congress. They should bode well for Republican efforts to gain the six seats needed to win control of the Senate in November.
How much it will help, though, remains debated.
Democrats argue that Republican candidates have won in large...