There is a political subtext to the definition of "middle class". Some politicians run on class warfare and say the rich are not paying their fair share (without defining what a fair share would be -- it's always more). So designating someone as "rich" means that you can gouge them. The president seems to use $250K for a married couple as the benchmark for "rich". Another phrase the class warriors love is "working class", although upper-income households tend to have more adults actually working full-time than lower-income households do.
My wife and I work full time and expect our children to do so when they grow up. Although our income is a multiple of the family median, we want our children to have a middle class mentality. They think going to Denny's is a real treat. So far, so good.
