Thirty-five Senate contests and thirty-six governorships are on the 2026 ballot. Twenty-six states have both.
Alabama, Alaska, Arkansas, Colorado, Georgia, Idaho, Illinois, Iowa, Kansas, Maine, Massachusetts, Michigan, Minnesota, Nebraska, New Hampshire, New Mexico, Oklahoma, Oregon, Rhode Island, South Carolina, South Dakota, Tennessee, Texas and Wyoming, plus Florida and Ohio, where the Senate seats are special elections for appointed incumbents.
Why this is a coincidence
The Senate list is fixed by the Constitution. Class 2 was elected in 2020 and its six years are up, and nothing about a state's politics or population can move it. The governor list is fixed by fifty separate state constitutions, most of which settled on four-year terms in midterm years for reasons that had to do with keeping state races off the presidential calendar.
Neither calendar consults the other. The twenty-six-state overlap in 2026 will be a different set in 2028 and a different one again in 2030.
What the overlap actually buys
A state with both races gets one field operation instead of two. The voter file work, the canvass, the mail program and the get-out-the-vote push are shared, and a door knocked for the Senate candidate is a door knocked for the governor. That halves the marginal cost of the second race and is the reason party committees look at this list before they look at polling.
The nine Senate-only states are Delaware, Kentucky, Louisiana, Mississippi, Montana, New Jersey, North Carolina, Virginia and West Virginia. The ten governor-only states are Arizona, California, Connecticut, Hawaii, Maryland, Nevada, New York, Pennsylvania, Vermont and Wisconsin. In both groups the statewide campaign carries its own turnout cost alone.
Whether that changes any outcome is genuinely unsettled in the political science literature, and I am not going to claim it from a table of dates.