However, in 2016, Republicans will go from being on the offense to being very much on defense. This is because the set of Senate seats that will be up in 2016 were last up in the GOP wave election of 2010, causing Republicans to have 24 seats to defend compared with only 10 for Democrats. Another key factor is that 2016 is a presidential year and will thus likely have a bigger and more diverse voter turnout that will favor Democrats.

What’s more, seven of the GOP seats are in states that Obama carried in 2012. In Illinois, where Mark Kirk will be up for reelection, Obama won by 17 points.

Four Republicans will be on the ballot in states where Obama prevailed by between 5 and 7 points: Kelly Ayotte (New Hampshire), Chuck Grassley (Iowa), Ron Johnson (Wisconsin), and Pat Toomey (Pennsylvania). In two other states where Republicans will be up, Obama eked out narrow wins: Marco Rubio (Florida) and Rob Portman (Ohio). Of the 10 seats Democrats are defending, none went for Romney in 2012; in fact, Obama’s worst margins of victory were still in the 5-to-7-point range: Michael Bennet (Colorado), Harry Reid (Nevada), and Ron Wyden (Oregon). Of these three Democratic incumbents, at least the first two can be expected to have aggressive challengers, but each last won under horrific circumstances for their party (the 2010 GOP wave), and in 2016, they will have a tailwind from the presidential turnout. On paper, anyway, the 2016 Senate elections look pretty good for Democrats, and if they head into Election Day with 48 or 49 seats, they would seem to have a pretty good chance of regaining the Senate.

Then comes 2018. It will be another midterm election, so turnout will benefit Republicans, and Democrats will have 25 seats to defend to just eight on the GOP side.