Leading up to the 2014 midterms, almost everyone acknowledged that the deck was stacked in favor of Republicans. That was especially true in Senate races where Democrats from some swing and red states who had been swept into office in the 2008 election of President Obama came up for re-election.
Going into the 2016 election, all that has been reversed. This time the odds favor Democrats. That becomes obvious when we take a look at Hotline's list of the of the 12 Senate seats most likely to flip. Keep in mind that these are listed in order of those most likely to flip party control.
1. Illinois - Mark Kirk (R)
2. Wisconsin - Ron Johnson (R)
3. New Hampshire - Kelly Ayotte (R)
4. Florida - Open (Marco Rubio -R)
5. Pennsylvania - Pat Toomey (R)
6. Ohio - Rob Portman (R)
7. Nevada - Open (Harry Reid - D)
8. Colorado - Michael Bennet (D)
9. Missouri - Roy Blunt (R)
10. North Carolina - Richard Burr (R)
11. Arizona - John McCain (R)
12. Indiana - Open (Dan Coats - R)
The first thing that strikes me from this list is that you have to get to number 7 before you find a possibility for a Senate seat to flip from Democrat to Republican. And there are only two of those on this list of twelve.
Secondly, the party that wins six of these twelve seats will likely control the Senate (depending on whether a Republican or Democrat is elected president). Since the overwhelming majority of these vulnerable seats are Republican, Democrats have many more chances to make that happen.
Finally, six of the incumbent Republicans (plus Marco Rubio) were elected to the Senate for the first time in the 2010 midterms when turnout was lower than during presidential elections and there was a wave of Republican revolt enflamed by the Tea Partiers. The larger 2016 electorate will test their staying power.
Of course, when discussing control of the Senate it is always important to remember that these days, having a majority means being able to name the Majority Leader and committee chairs. As long as the bar is set at a supermajority of 60 votes to actually pass legislation, the victory is limited. But right now, the odds of a limited victory in 2016 heavily favor the Democrats.