In northern states, there was a lack of interest, too. The overall vote total dropped by 42 percent compared with 2012, and the decline was particularly acute among younger voters, who made up 13 percent of this year’s electorate compared with 19 percent two years ago. The turnout among young and minority voters was slightly higher than it was in the 2010 midterms, perhaps reflecting new organizing efforts, but the number remained far too low. (Republicans have continued their effort to suppress the turnout of young, poor and minority voters, although it was hard to make a definitive link between those laws and Democratic losses this year.)

There was one useful lesson: When voting is made easier, more people vote. Colorado switched to a mail ballot system this year, and it had the fourth-highest turnout in the nation, substantially larger than in 2010. (It had a highly competitive Senate race, but did much better than many states with equally hot races.) Oregon, which also votes by mail, had the fifth-highest turnout, and Washington State, with a similar system, did better than the national average, though it had no major statewide races.