MADISON, Wis. — Wisconsin Republican Gov. Scott Walker has been warning for months about a “blue wave” coming this fall, but so many Democrats are eager to ride it that it is a struggle for any dominant challenger to emerge.

Eight Democrats are taking on Walker as he seeks a third term, a sign of just how badly the party wants to dethrone one of the GOP’s most recognizable governors. Walker’s strong anti-union moves made him a demon to the left and catapulted him to the national stage for a brief 2016 presidential run.

Superintendent of Public Instruction of Wisconsin Tony Evers, who has skirmished with Walker on a number of issues over the years, enters Tuesday’s primary as the best-known Democrat.