Sen. Chuck Schumer’s skills as a politician will be fully tested in the tightly controlled Senate, where the “filibuster” rule can make it difficult to pass any legislation with fewer than 60 votes, and where even measures that can be passed with a simple majority will have to please the most conservative Democrats in the body. “Schumer is constrained both by the filibuster and also the preferences of his least-liberal members,” said Kyle Kondik of the University of Virginia Center for Politics. “That list starts with Sen. Joe Manchin of West Virginia.”