This year, 43 states are holding regularly-scheduled state legislative elections. There are 5,984 seats up. Democrats have 4,720 nominees, and Republicans have 4,859 nominees. In Washington and California, candidates with a major party label are assumed to be “nominees”, and in seats in which two Democrats are the only candidates on the ballot, the Democratic Party is given credit for one “nominee”; the same rule applies to Republicans, of course.
Because Democrats are lacking a nominee for 1,264 seats, and because Republicans are lacking a nominee for 1,125 seats, that makes 2,389 seats with no Republican-Democratic contest. Ballot Access News has been tracking this data starting in 1992, and never before has the proportion of no-major party-contest seats been so high. 2,389 works out to 39.9% of all the seats.
States in which the Democratic Party doesn’t have nominees for even half the seats are Georgia, South Carolina, and Wyoming. States in which the Republican Party doesn’t have nominees for even half the seats are Massachusetts and Rhode Island.