The Democrats’ midterm drop off problem is as well understood as it is intractable. For a number of reasons, young adults and minorities are less likely to vote in midterm elections than in general elections, and since young people and minorities vote disproportionately for Democrats, while old people vote disproportionately for Republicans, Democrats perform significantly worse in midterms than in general elections.

[…]

it’s not quite as straightforward as making unreliable voters more reliable. For every unit of energy and resources Democrats devote to reduce the difference between their midterm and general electorates, Republicans are responding—not with turnout-boosting strategies of their own, but by making it harder for the pool of voters who make up that difference to vote, even if they want to.

Frankly, I think attempts to suppress the vote, rather than encouraging all eligible voters to get out there, are the sign of a dying political party.

See here for more.