The 2014 midterms were a perfect storm for Republican candidates. Six years ago, Democrats swept into power across the nation boosted by disgust with George W. Bush and unprecedented enthusiasm for candidate Barack Obama. This week, that huge overhang of seats became a vulnerability, forcing the Democrats to play defense in many tough states. And enthusiasm for Obama was a thing of the past. The unpopular incumbent president powered conservative turnout, while the midterm setting was unfavorable for the Democrats' boom-and-bust coalition.
But after the bust comes the boom. Obviously the ultimate outcome in the 2016 election depends on inherently unforeseeable events, but the fundamentals of the race should look very different — and much less favorable to Republicans. But then it's all going to flip again two years later.
1) The 2016 map is way better for Senate Democrats
The Senators up for re-election in 2016 will be the ones who took office in 2010 and 2004, both strong years for the GOP. That means Republicans will be playing defense. Illinois is very likely to go to the Democrats. Wisconsin and Pennsylvania are both states with substantial blue tints. The seats in Ohio, Iowa, New Hampshire, and Florida are all very winnable for Democrats, and Missouri, North Carolina, and Arizona are on the board as reach possibilities. Republicans, by contrast, really only have a single pickup opportunity in Colorado.
Even if everything goes great for the GOP campaign-wise, it's hard to imagine them picking up seats, while Democrats are likely to get two or three and could plausibly snag many more than that.
2) The 2016 electorate will be more liberal
More people vote in presidential elections than in midterms. And the non-participation is not evenly distributed. Younger people and non-whites are especially unlikely to vote in non-presidential years, and 2014 was no exception to this rule. Since younger people and non-whites tend to vote for Democrats, this means that closely divided states such as Ohio, Florida, Iowa, and New Hampshire have an electorate that leans Republican in midterms and Democratic in presidential years.
This is great news for the Democratic presidential nominee in 2016 (I hear Hillary might run), as well as for various candidates for lower office.
3) The economy is getting better
This one is less certain, but one dog that didn't really bite in the 2014 election is the basic reality that by most measures the long-ailing economy is getting better. Democrats didn't get much of a lift from that yet, in part because the economy is still pretty bad. The unemployment rate is lower and GDP is higher, but so far most of the gains from the recovery have accrued to people who own stock rather than people who work for a living. But there's lots of evidence that this is about to change, and the unemployment rate has finally dropped low enough that employers are facing pressure to start paying more.
Things could easily take a turn for the worse over the next two years, but there are reasons to think the recovery will continue. Slowing growth in China and increasing oil production at home mean that gas prices won't pinch consumers the way they have in the past. And the Federal Reserve shows no sign of being too eager to raise interest rates. By 2016, it's likely that the "improving economy" story will actually be real for middle-class Americans.
4) In 2018, it all flips again
The joke on America, however, is that four years from now everything will flip again. The 2018 Senate map isn't quite as extreme as the 2012 or 2014 maps, but it's pretty clearly tilted in favor of Republicans. And the midterm electorate will also favor Republicans. I'm not nearly crazy enough to pretend I can tell you how the economy will be doing by 2018, but suffice it to say there is no historical precedent for the economy lasting that long without a recession.
Demographics aren't strictly destiny. Democrats won big in 2006 despite the midterm electorate and a not-so-friendly map. Events matter. Nobody knows what will happen between now and then. But the 2016 fundamentals will tilt the playing field heavily in the Democrats' direction, while 2018 will do the reverse.
And in a sense, the "endless seesaw" model of American politics makes perfect sense. The presidential and non-presidential electorates look too different for either political party to optimize for both of them. Democrats have built a coalition that's optimized for presidential years, while the GOP has one that's optimized for off-years. And so we're set for a lot of big swings back and forth every two years.