Democrats said they were focused on mobilizing existing voters rather than registering new ones, but they also pointed to data from TargetSmart, a Democratic polling firm, suggesting that newly registered voters in Pennsylvania were more likely to vote Democrat than Republican.
Brendan Welch, a spokesman for the Pennsylvania Democratic Party, said that Republicans’ gains could be traced to voters who were previously registered as Democrats but who had voted Republican for years, and cited Republican registration increases in counties that Mr. Trump carried in 2016.
“These are mostly the kind of folks who have been registered Democrats since the days of Jimmy Carter vs. Gerald Ford, but who have been voting Republican since the days of George Bush vs. Al Gore,” Mr. Welch said.
A similar dynamic may be at work in North Carolina, where Republicans have narrowed the gap in registrations. Records show Democrats lost 136,000 voters since 2016 while Republicans gained 100,000, though Democrats still lead in overall registrations by 400,000, with 2.6 million Democrats and 2.2 million Republicans.
The Democrats’ overall loss in the state stems from a 2019 purge of inactive voters that disproportionately affected Democrats, said J. Michael Bitzer, a professor of political science at Catawba College in North Carolina. Some 235,000 Democrats and 146,000 Republicans were removed from the rolls.
Since 2016, Dr. Bitzer said, Democrats have shown gains by another metric — the number of newly registered voters in the state.
“The national narrative of simply taking the net numbers of registered Democrats and Republicans in this state belies the fact that among new registered voters, Democrats have, in total, held their own against Republicans,” he said.