In the 2016 cycle, Democrats are defending only 10 seats while Republicans have two dozen of their own seats to hold. 7 of those 24 Republican seats are in states that President Obama won twice: Florida, Illinois, Iowa, New Hampshire, Ohio, Pennsylvania and Wisconsin. To win the majority back, Democrats need to win five of those seven seats in November 2016. (If a Democrat, wins the White House in 2016, then Senate Democrats need to win only four of those seven. That's the exact path Republicans took to the Senate majority in 2014 when, needing a six-seat gain, they won...