Income and the Middle Class

I've read several posts and comments recently about how both President Obama and Governor Romney are talking about the "middle class"  (see this post over at Economix by Catherine Rampell).  I suppose there isn't a widely accepted standard definition in use here, but I find it bothersome when both candidates refer to "people with incomes less than or equal to $250,000 as "middle class."  Using data from the Tax Policy Center (see here), I generated the graph below:

Note that $250,000 of income is about the 96th percentile (clearly not anywhere near the "middle").  Thus I do not know in what sense this is meaningfully viewed as middle class.