The race for Senate control is expected to be close. It may just hinge on a seat or two either way.
Here is a primer on phenomena to track as the Senate returns roll in.
Republicans hold a 54-46 seat edge in the Senate now. Two independents, Sens. Bernie Sanders, I-Vt., and Angus King, I-Maine, caucus with the Democrats.
Approximately a third of the Senate is up for reelection every two years. 2010 was a big year for Senate Republicans – even though they fell short of control.
As a result, Republicans are defending 24 of the 34 seats in play this cycle. 2010 was not only a “Republican” year in Senate contests but a midterm year. Those two factors work directly against the GOP this year as freshman, Republican senators who won in 2010 now find themselves on the ballot in battleground states in a presidential election year.
Consider the competitive races facing Sens. Kelly Ayotte, R-N.H., Pat Toomey, R-Pa., and Ron Johnson, R-Wis. All are in states that are barnburners at the presidential level. This factor alone is one of the reasons the GOP majority is at risk. The electorate is a lot different in the presidential atmosphere of 2016 compared with the Tea Party-infused playing field of the 2010 midterm.
The other issue is that Republicans only have one seat they may be able to seize from Democrats. That seat’s in Nevada as Rep. Joe Heck, R-Nev., runs against Democrat Catherine Cortez Masto. Senate Minority Leader Harry Reid, D-Nev., is quitting. Otherwise, Republicans play defense across the board.