Another poster types this:
"but we've seen registered independents and swing voters move away from the Democrats in recent years."
I respond with an appropriate, recent poll showing otherwise.
You respond with a non-sequitur.
But since we are changing topics, I'll play.
How do I explain the republican trouncing in 2014? I explain it the same way I explain the republican trouncing of 2010, or the democratic trouncing of 2006 or just about any off-cycle election of the party not in the white house going back decades with few exceptions...particularly at the 6 year mark.
I explain 2016 the same way I explain 2012 and 2008, the dems do better in presidential years because young people and minorities are more likely to vote in a presidential election and that bleeds over into congressional races. republicans do better in off-cycle elections, particularly when they don't control the WH because those electorates skew older and whiter and more male most of the time.
There are exceptions as always, but that is a general pattern that holds up pretty well.
I expect a dem victory across the board in 2016 (except redistricting means it's almost impossible to win back the house). I expect the republicans to make back gains in 2018 in the senate (although I haven't looked to see which 33 percent of seats are in play). IOW, I expect the pattern to hold because I don't see anything transformative to break that pattern one way or the other.
You're partially correct, but I did find this article on Nate Silver's 538 blog.
http://fivethirtyeight.com/datalab/voters-were-just-as-diverse-in-2014-as-they-were-in-2008/
Here's a quote from that article "That’s partially because 18- to 29-year-old voters who turned out in 2014 voted Republican by 23 percentage points more than 18- to 29-year-olds in 2008.3" There's also some statistics in that article that show a slightly higher percentage of Blacks, Hispanics, and Asians voted Republican in 2014 versus 2008. I'm sure you can argue the point that events or actions since 2014, by Trump as well as other Republican candidates, might very well chase some of those voters back to the Democrat candidate. But it also shows some of the minorities are willing to consider a Republican candidate if they don't see a slam dunk choice on the Democrat side, one that might have some baggage or slightly higher than normal disapproval ratings with Democrat voters(Hillary?).