One way to measure voter enthusiasm is to compare voter registration trends for each party. A Democratic strategist who closely follows the data on a day-to-day basis wrote in a privately circulated newsletter:

“Since last week, the share of white non-college over 30 registrations in the battleground states has increased by 10 points compared to September 2016, and the Democratic margin dropped 10 points to just 6 points. And there are serious signs of political engagement by white non-college voters who had not cast ballots in previous elections.”

David Wasserman, House editor for The Cook Political Report. wrote on Oct. 1 that voter registration patterns over a longer period in key battleground states show that “Republicans have swamped Democrats in adding new voters to the rolls, a dramatic GOP improvement over 2016.”

Four of the six states Trump won by fewer than five points in 2016 allow voters to register by party: Arizona, Florida, North Carolina and Pennsylvania. In recent months, there have been substantially more Republicans added to the rolls than Democrats in each of them except for Arizona.