Who cares?

President Obama. AP Photo.

That's a common reaction -- particularly in the Democratic wing of the Twitter-sphere -- anytime, like this morning, we post a piece detailing President Obama's sinking poll numbers. The thinking goes something like this: Obama isn't ever going to have to run for reelection again, so focusing on his poll numbers -- whether good or bad -- is a meaningless exercise by political journalists.

Except that it's not. At all.

Take a look back at the election results from the second midterm elections of presidents, which is what 2014 will be. From the end of World War II until the 1986 election, the president's party lost an average of 48 seats in the House and seven seats in the Senate, according to the indispensable congressional analyst Norm Ornstein.  That "six-year itch" trend has slowed in more recent second-term midterm elections -- the average losses for the president's party in the 1986, 1998 and 2006 midterms is 10 seats in the House and four seats in the Senate --  but the pattern of losses remains. (In only two six-year-itch elections since the Civil War -- one of which happened in 1998 -- has the president's party not lost seats in Congress.)

There is a panoply of theories to explain the historical consistency of the six-year itch. Here's Fix mentor and nonpartisan political handicapper Charlie Cook's explanation:

When a president is elected, he is full of energy and new ideas. There is an excitement surrounding the election of a new commander in chief in the first couple of years and a considerable amount of momentum. In the third and fourth years, all of those favorables are harnessed in reelecting the president. In their fifth and sixth years, presidencies tend to run out of gas and new ideas, and their novelty has worn off. The public begins to gradually and increasingly grow weary, resulting in bad six-year itches.

Here's our take: It's impossible to separate out how a president is doing in the eyes of the public from how voters will judge his party -- even, and maybe especially, in an election in which his name is not actually on the ballot.  The relatively minor losses incurred by Ronald Reagan in 1986 and Bill Clinton's history-making gains in 1998 came as both men were remarkably well-liked by the general electorate.  In 2006, a deeply unpopular George W. Bush watched his party lose 30 seats and control of the House. Check out this chart from Robert Blizzard, a Republican pollster at Public Opinion Strategies, that details the arc of presidential approval in second terms.

Image courtesy of Public Opinion Strategies

The similarities between Bush's trend line and Obama's should be a major concern for Democrats hoping to hold the Senate and retake the House next year. And, already there are signs of real worry among Democrats who will be running for reelection in areas that are less-than-friendly to the president. Georgia Rep. John Barrow, who represents a district that gave Mitt Romney 55 percent in 2012, became the first Democrat to sign on to a Republican-led House effort that would allow those who wanted to keep the insurance they had prior to Obamacare to do so. In the Senate, Louisiana Democrat Mary Landrieu is spearheading a similar effort amid signs that Obamacare could jeopardize her chances at a fourth term next November. And, Landrieu was one of 16 Democratic senators -- a group that included other 2014 targets like Mark Begich of Alaska and Mark Pryor of Arkansas -- to visit the White House last week to voice concerns about the troubled rollout  of Obamacare.

So, no, President Obama doesn't need to worry about how his sinking job approval -- and personal favorability -- numbers will impact his future races. But, if you believe that at least some portion of a president's legacy is built on -- or broken by -- the state he leaves his party in when he departs office, then Obama's poll standing matters a whole heck of a lot as we get closer and closer to 2014.

The loss of the Senate majority and a smaller minority in the House after November 2014 would make any attempt to rack up second-term accomplishments before he left office extremely difficult for Obama. Combine that with the reality that Obama's second term has not exactly been larded with major wins to date and you understand why Obama and his legacy are on the ballot in 2014 -- even if his name is not. And that means his poll numbers matter. A lot.