A theory for how to win the 2020 presidential election has quickly become conventional wisdom among Democratic campaign strategists and many prominent pundits. It goes like this: The country has become so polarized that swing voters barely exist anymore. Elections are now decided by which side better manages to mobilize its base. So Democrats need to stop worrying about winning over moderates—and confidently move to the left.

Proponents of this “progressive mobilization theory” can point to a few important pieces of evidence. Plenty of liberal policies, for instance, are popular with voters across the political spectrum. As I’ve argued in the past, this makes it possible for Democratic presidential candidates to develop an ambitious agenda on issues from health care to gun control without jeopardizing their chances of ousting Donald Trump.

But the theory is nonetheless wrong in three crucial respects. A significant number of swing voters do exist, and in close-run elections, they matter. While Democrats do need to mobilize their base to win in 2020, it is far from obvious that moving to the left will help them do so. And to cure America of Trumpism, they need to persuade voters who aren’t already consistent progressives to turn their back on his brand of politics.

https://www.theatlantic.com/ideas/archive/2019/10/problem-mobilization-theory/599236/