Republicans have a 33-16 advantage in gubernatorial offices; Alaska's Bill Walker is an independent. The most competitive of 2018's 36 gubernatorial races:
Colorado
Democratic Gov. John Hickenlooper is term-limited. The field of candidates in both parties is expected to be large and the competition to be wide open. The state has trended Democratic in recent elections. Primaries are June 26.
Connecticut
Gov. Dannel Malloy, a Democrat, decided not to seek a third term. There are no clear front-runners as Democratic Lt. Gov. Nancy Wyman and House GOP Leader Themis Klarides weigh their plans. Primaries will be Aug. 14.
Florida
Gov. Rick Scott, a Republican, can't run again because of term limits. Democrats last won the governorship in 1994, but recent contests have been narrowly divided. Climate change is a big issue. Primaries are Aug. 28.
Illinois