Taken together, of the 170 contested elections that have been held this year for state legislative seats, for federal office, or for statewide office, the Democrat ran ahead of President Obama’s 2012 showing in only 27 races. By contrast, the Democrat ran more than 10 points behind the president’s showing in 47 races. On average, Democrats ran 5.9 percentage points behind the president, with a median drop-off of 6.4. Even if we knock a point off of these numbers to account for the Chris Christie effect in many of these races, that’s still a big decline.

What does this mean for 2014? Possibly nothing. There is a lot of football left to be played, the president’s job approval rating could rally significantly, the Democrats could become enthused, and drop-off could become a non-issue.

But if that doesn’t happen, Democrats have a real headache coming on. Let’s assume they can expect a drop-off of four to five points from Obama’s 2012 performance, all other things being equal. Twenty-eight House Democrats occupy seats where Obama won less than 55 percent of the vote. More disturbingly for Mr. Jackson’s Party, 13 Senate seats fall into this category. This is consistent with what we’ve seen in polling: Democrats putting up terrible numbers in places like Louisiana, Arkansas and North Carolina, while races in states like Michigan and Iowa are looking surprisingly tight.