For former Massachusetts governor Mitt Romney to win in four weeks time, he needs voters to have a single question on their minds when they enter their polling place: "Am I better off than I was four years ago?"

There are all sorts of data points that both parties cite to answer that question (for Democrats it's private sector job creation, for Republicans it's things like the soaring number of people on food stamps) but one really good way to look at the "are you better off" question is to compare how much a family was making four years ago to how much they are making today.

Thanks to the Post graphics department we now have that information in a single chart. Below is the median household income from 2007 to 2011 from the 14 most competitive states at the presidential level. (The 2012 data isn't yet available from the Census Bureau.)

In all 14 states, median income has dropped over that time -- as it has nationally. In 12 of the 14, median household income also dropped between 2010 to 2011 with the most precipitous declines in Nevada (down six percent) and Florida (down three percent). Only in Iowa and Wisconsin did median household income rise between 2010 and 2011.  (To see median household income in all 50 states, check out the complete chart here.)

The drop in median household income shows the political headwinds that President Obama has been running into in his re-election bid. With less money coming in than was coming in four years ago, it's tough to believe the argument that things are (slowly but surely) getting better.

To be clear: Simply because a state's median household income has dropped doesn't mean President Obama will lose it.  New Mexico, for example, appear to be comfortably in Obama's camp. But, the drop in median income should allow Romney the chance to make a strong closing argument centered on the "are you better off?" argument.