Democrats’ strategy for winning in 2020? Policy, and lots of it.

There’s a long, long way to go before the 2020 presidential campaign draws to a close. Early-round primary voting is still nine months away, and the field of Democratic hopefuls stands at nearly two dozen, with even more contenders poised to enter.

And although the average American is far more engrossed in the final season of Game of Thrones than the preliminary jockeying among presidential aspirants, the campaign goes on. And on.

So just how do a swelling numbers of De...