Rep. Chris Van Hollen (D-Md.), the chairman of the Democratic Congressional Campaign Committee, will travel to Ohio and Nebraska this week to help two Democrats who are in tough re-election fights and two others who are trying to unseat Republicans.Van Hollen on Thursday will be in Ohio to help raise money for Reps. Steve Driehaus of the Cincinnati-area 1st district and Mary Jo Kilroy of the Columbus-based 15th district. Both are in tight races against the Republicans they defeated in 2008: Driehaus is up against former Rep. Steve Chabot, and Kilroy will again face Steve Stivers, a former state Senator.Van Hollen also will appear at a fundraiser Thursday to benefit Paula Brooks, a county commissioner in Columbus who is trying to unseat Rep. Patrick Tiberi (R) in the 12th district. Tiberi is well-funded.On Friday, Van Hollen will be in Nebraska to raise money for Tom White, a lawyer and member of the state’s unicameral legislature who is running against Rep. Lee Terry (R) in the Omaha-based 2nd district.