The outcome of four races could determine whether the Washington remains in Democrats ' hands . Arkansas : Even with the Clinton machine rallying to his side , Democratic Sen. Mark Pryor has been struggling against GOP Rep. Tom Cotton , a veteran and Harvard graduate who has been hammering away at Pryor for his ties to President Obama , a common theme on the campaign trail . Julian Zelizer : Democrats citing GOP extremism ; Republicans cite White House 's performance . In six of the states , Democratic incumbents are seeking to win re-election . Zelizer : Can Obama reverse historical pattern of midterm losses ?
The outcome of four races could determine whether the Washington remains in Democrats ' hands . Julian Zelizer : Democrats citing GOP extremism ; Republicans cite White House 's performance . In six of the states , Democratic incumbents are seeking to win re-election . Zelizer : Can Obama reverse historical pattern of midterm losses ?