The best way to increase voter turnout is the systems they have on the west coast like CA, OR & WA. Everyone is auto registered, everyone gets a ballot mailed to them along with info about the candidates. You fill the ballot out and either put it in the mail, or you can drop it off at a ballot box.
Voter turnout in WA was 79% in 2024. Nationwide voter turnout was 64% in 2024.
But you’re not asking about turnout in general, you’re asking about democratic turnout. Sadly ~85 million may be the cap. Biden got 81 million in 2020, and Harris got ~75 million in 2024.
I made a post here discussing how even though Harris lost 6 million votes vs Biden, over half of that was in 4 blue states that went for Harris anyway. A lot may have been democrats protesting by not voting over Gaza and economic issues, knowing that their state electoral votes would go to Harris anyway.
I feel like even with the perfect candidate, perfect momentum, etc the democrats are going to peak at about 85 million votes. Even then the GOP could run Hitler’s missing testicle on a pro-NAMBLA, pro-’death penalty for being poor’ platform and they’d also get 80 million votes.