Sabato’s Crystal Ball spells it out:
The 2014 midterm, no matter the outcome, does not hold real predictive value for 2016. We’ve often compared this year with 1986, where Democrats bounced back to capture the Senate on a highly favorable map in President Reagan’s “sixth-year itch” second midterm. Of course, two years later, the country elected a Republican president for the third straight time. Could the current GOP meet with a similar fate? The results next Tuesday certainly won’t tell us.
Alternately, 2014 might prove to be like 2006, a great Democratic year that foreshadowed another great Democratic year. For all the legitimate talk of the Democrats’ growing demographic edge in presidential elections, the advantage could be blunted by an unpopular President Obama, who like then-President George W. Bush could drag down his party in consecutive elections. Obama’s approval rating is very important in the outcome of the next presidential election: If his approval rating continues to stagnate or sinks even lower, his standing will once again imperil Democrats, just as it did in 2010 and 2014. Democrats in and out of Congress will need to find ways to help Obama leave office on a high note, because their fortunes — and that of the Democratic nominee picked to succeed him — will still be linked to his.