What to Watch For as G.O.P. Expects Big Night at Polls-NY Times

"To gauge Republican strength, watch the Senate races in states that President Obama won in 2008 or 2012. If Republicans, who need to pick up six seats to gain the Senate majority, win in Colorado, Iowa, New Hampshire and North Carolina, they are all but certain to take control. If they lose them all or split them, the fate of the Senate may not be known for some time."