And after five tough years of a recession and slow economy, there's plenty of evidence that fewer people see a middle-class life when they look in the mirror.

“You can’t define middle class, but you can ask people, ‘Do you still feel middle class?’ And more and more people don’t,” said Tim Smeeding, director of the Institute for Research on Poverty at the University of Wisconsin.

Still, as election season heats up, that’s not stopping many politicians from promising to help the middle class, whoever they may be.

"The whole attraction of middle class … is it doesn’t mean anything," said Dennis Gilbert, a sociology professor at Hamilton College who studies class issues. "Middle class means anybody who might vote for you."

The focus on the middle class starts at the top of the ticket, where President Barack Obama and Republican challenger Mitt Romney have both repeatedly invoked the middle class in their quest to win the presidency next month.

Obama told voters during last week's debate that he cut taxes for middle-class families “because I believe that we do best when the middle class is doing well.”

Then he questioned whether Romney had the same dedication to the middle class.

“And at some point, I think the American people have to ask themselves, is the reason that Governor Romney is keeping all these plans to replace secret because they're too good? Is it -- is it because that somehow middle-class families are going to benefit too much from them?” Obama said, according to a transcript provided by the Commission on Presidential Debates.

Romney argued that Obama’s policies have hurt the middle class and would continue to do so.

“There's no question in my mind that if the president were to be re-elected you'll continue to see a middle-class squeeze with incomes going down and prices going up,” he said during the debate. “I'll get incomes up again.”