The Democrats will claim (as Republicans did in the second mid-term of George W. Bush's Presidency) that Obama isn't on the ballot and that the opponent needs to run against "ME" not the President.
It is not clear that a modestly unpopular Obama will do much to change the landscape, but it will almost certainly have a negative effect on Democratic turnout -- notwithstanding what I (incorrectly) thought would happen in 2012.
But the Dems will be correct: Obama will NOT be on the ballot to create enthusiasm and drive turnout. That will be up to individual candidates and, absent a so-far undetected wave in November 2014, it will create a higher electoral hill for Democrats to climb.
If Syria continues to rage, if Iran goes nuclear, if Egypt and Turkey continue their slides from secular to Islamic societies, and if any one of a dozen potential hot-spots flare up over the next 17 months, then Obama's ability to demonstrate leadership in foreign policy might be forever shattered.
If the overall unemployment rate remains above seven percent -- the last time it was below was in November 2008 -- then the young people for whom unemployment is especially vexing may not turn out to vote Democrat. From a New York Times article from last month:
"According to the Labor Department, workers 25 to 34 years old are the only age group with lower average wages in early 2013 than in 2000."
Minority unemployment in May was almost double the overall rate -- 13.5 percent.
Someone who will be 25 years old in 2014 was only 11 when George W. was first elected in 2000 and was just out of high school when Obama was sworn in. Sitting in their parents' homes watching Law & Order reruns is not likely to prompt them go out and work for Obama's Democrats next November.
We'll see if these numbers continue to weigh on Obama, but there doesn't appear to be much on the horizon to put wind in his Presidential sails.