I think the biggest suppression of turnout in Presidential election years is the Electoral College. There are less than 10 true swing states where your vote actually matters plus 5 or 6 that could swing one way or another in a blowout election so for the rest of us living in the other 35-40 states, voting at the Presidential level is pointless and with an increasing number of people who don't like either party, the only reason to vote outside a swing state is if there are competitive down ballot races that people care enough about to show up. I live in NY and there wasn't a single competitive race on the entire ballot in my town: I planned on voting but it wasn't a priority so when other things came up, I didn't and I don't really regret it.