I think it is actually lower class when one can't get ahead of their debts and can't enjoy the nicer things in life. I am middle-class, debt-free, retired and comfortable while living in my home that is better than my parents' home. My adult kids are having a tougher go at life, having to work hard and trying not to get into debt while raising their kids - I consider them to be middle-class. Others that are working poor with a huge debt-load that can't be surmounted, I would call lower class. I have relatives in that situation who have lost their homes during the Obama reign. They have certainly fallen into the lower class.
I don't think there's anything "lower class" about carrying a pile of student debt for a college education of questionable worth, or carrying ridiculous mortgage on an overpriced home, or paying off a seven-year loan on a car you never should have purchased.