If history is any guide, Democrats are headed toward a tough midterm election this fall -- and nowhere will it be worse than at the state legislative level.

Political junkies are familiar with the so-called "six year itch" effect in federal elections. If you're not, it goes like this: The party of a re-elected president tends to get walloped in the following midterm election. Since 1912 (that's when the House expanded to 435 seats), the president's party has lost an average of 29 House seats in the following midterm election. (As Aaron Blake notes, however, that is a smaller number of seat losses than presidents have averaged in the midterm election of their first term.)

It turns out that the six-year itch is even more devastating at the state legislative level, which, as we documented in a post late last week is a critical piece of the political and policy equation for both parties nationally.  Check out this chart, courtesy of the National Conference of State Legislators, to grasp just how daunting the history of second term, midterm elections are for the president's party at the state legislative level.

Image courtesy of NCSL

"Since 1902, the party in the White House lost seats in legislatures in 26 of the 28 mid-term elections," said NCSL's state legislative race expert Tim Storey. "The only exceptions being in 1934 when Democrats gained 1108 seats and in 2002 when Republicans netted 177 seats in the post 9/11 election."

Storey notes that because of the massive gains Republicans made at the state legislative level in 2010 -- the GOP went from full control of 14 legislative chambers before the election to 25 after it --  there will be far less low-hanging fruit then in a typical six year itch election. And, if Obama is able to genuinely bend his party's focus all the way downballot in 2014, then it's possible this November could be an anomalous year.

But, the weight of history is heavy in this one. And that's worrisome for Democrats.