In the Times/Siena-based estimates, Democrats appeared to be at a turnout advantage in the Rust Belt in the midterms but at a disadvantage in the Sun Belt. The difference between the groups of states might seem small, but it is not. A hypothetical full-turnout election among registered voters would cut this difference in half, and a full-turnout election among all eligible voters might eliminate it entirely.

This is consistent with state-by-state surveys of adults, like a 2019 compilation of Gallup polling data that showed the president’s approval ratings in Florida, Texas, Wisconsin, Michigan and Pennsylvania all crowded together between 41 percent and 43 percent, a few points higher than the 40 percent he held nationwide in the poll.

The danger for Democrats is that higher turnout would do little to help them in the Electoral College if it did not improve their position in the crucial Midwestern battlegrounds. Higher turnout could even help the president there, where an outsize number of white working-class voters who back the president stayed home in 2018, potentially creating a larger split between the national vote and the Electoral College in 2020 than in 2016.