Four of the 25 states that have held primaries so far allow same-day registration. All saw turnout decline between 2010 and 2014. Oregon, which uses mail ballots, saw record-low turnout. California, where two-thirds of voters mail in their ballots, saw the lowest turnout ever.

The results in states that allow in-person early voting or no-excuse absentee voting were no more encouraging. Eight states that have held primaries this year employ both procedures. Two saw turnout increase; six had record lows.

“The numbers in this report reflect how deeply citizens are turning away from political engagement and from positive feelings about one or another major political party,” wrote Curtis Gans, the center’s longtime director.