Mitch McConnell might not want to get too comfortable if he becomes Senate majority leader this January.
A favorable Senate map and political landscape have put Republicans on the cusp of winning back the majority they lost eight years ago, but their control of the chamber is likely to be in jeopardy almost from the moment the 114th Congress gavels into session.
Just as Democrats have had to protect seats this fall in deep red states captured in the wave year of 2008, Republicans in the next congressional elections will be defending territory they won in blue and purple states during their own sweeping victory in 2010.
"It's important for Republicans to do as well as they possibly can this fall, because the 2016 election is going to be fought on much different terrain," said Nathan Gonzales, a political analyst at the Rothenberg Political Report.
Senators Ron Johnson of Wisconsin, Pat Toomey of Pennsylvania, Kelly Ayotte of New Hampshire, Mark Kirk of Illinois, Rob Portman of Ohio and Marco Rubio of Florida all will be seeking second terms in states won by President Obama in 2012. Rubio is eyeing the White House and might not run for reelection at all, having said he won't seek both offices at the same time.