In a campaign season with broad presidential implications, Democrats are working to undercut prominent Republican governors who expect to strengthen their political appeal in November's midterm elections.
Democrats have few opportunities to improve their numbers in the Senate and House, but leaders in both parties acknowledge that Democrats have a natural advantage in races for governor.
Republicans have to defend 22 of the 36 seats up for election, including six in states that President Barack Obama carried twice: Ohio, Michigan, Pennsylvania, Florida, Wisconsin and Maine.
Democrats have sought to tarnish New Jersey Gov. Chris Christie as he deals with home-state scandals. They hope to extend the scrutiny to Wisconsin Gov. Scott Walker and Ohio Gov. John Kasich. All three are potential contenders for the GOP presidential nomination.