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Vice President Joe Biden, left, complained Republicans are holding hostage a middle-class tax cut. Republican contender Paul Ryan pledged to retain middle-class tax preferences.

"Middle class" has no formal definition, but it's fair to say politicians know a key voting bloc when they see one.

Vice President Joe Biden and his Republican rival Rep. Paul Ryan used the term more than 30 times in Thursday night's vice presidential debate, with both candidates pledging to cut taxes for the elusive center.

We asked TODAY.com readers to tell us how they define the middle class, and their responses were about quality of life as much as about income: The ability to pay your bills on time, at least most of the time. The aspiration to send your children to college. The idea of being better off than your parents.

Many told us they equate middle class with financial security, although they differed on how much security you need to fall into middle class spectrum.

“I really define middle class as someone that owns their own home, has at least two cars, pays their bills on time, and can afford to buy things without having the charges sit on credit for a long period of time,” wrote James Gunnarson, 37, a system administrator from Bridgetown, Ohio.

Gunnarson said in an e-mail that he consider himself and his wife to be on the higher end of middle class because they can afford most things they need without too much financial hardship. He doesn’t give politicians credit for his family’s success.

“We got to this point by making the right decisions, not by tax cuts or politicians,” he wrote.

Others said you can be less financially secure and still qualify as middle class.

Frances Eve Salinas, 32, of Dallas, wrote that middle class is “the area in between living financially comfortably and worrying if the rent check will bounce.”

“I see myself as middle class based on this concept: I earn enough money to live – week by week. No more, no less,” said Barb Witkow, 60, who lives in Bellevue, Wash., and works as a psychotherapist.

Witkow makes about $85,000 a year, but she pays about $2,000 a month in student loan and credit card payments and another $1,100 for rent. That leaves her with little for extras like clothes or vacations, let alone bigger expenses like health insurance. She shares a home with two other women and expects to work until she is 75 or 80.

“I dwell in the MIDDLE – getting by. I (feel) blessed that I have this status of being able to survive, AND saddened that I can only get by,” she wrote to TODAY. 

Many readers said they were grappling with a feeling of slipping backward.

Ann Lowe, 35, said she grew up in a middle- to upper middle-class home, but the economic struggles of recent years have left her feeling more like she is closer to lower middle class.

Both she and her husband, who live in Charlotte, N.C., make less money than they once did and have put off starting a family and buying a home for financial reasons. By contrast, she said, her own parents seemed to be on a much better path by the time they were the age she is now.

“I am very hopeful that the economy will recover over the next few years and we will be able to see some degree (of) upward mobility in our lives, but with each passing year it is looking less and less likely that we will be better off than -- or even equally as successful as -- our parents,” Lowe wrote.

Jennifer Sale, 38, finds some comfort in the fact that there is no official cutoff for the middle class. Sale, a receptionist in Henrico, Va., struggles to pay her bills on time. She and her husband didn’t go to college, but she remains hopeful that their children will.

“I for one am glad there’s no definition for middle class. If I were told that my family was poor, it would be hard not to lose hope,” Sale, 38, wrote to TODAY.

Steven Hafner, 50, still thinks of himself as middle class, even though he has in recent years had to grapple with stagnant to declining wages.

Hafner, a research scientist who lives in Stafford Township, N.J., said that to him being in the middle class is about more than just wages. It’s also about education, social skills and  the support to continuously improve your lot in life.

“In a nutshell I define middle class as having the potential for upward mobility,” Hafner said.

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What is the middle class, anyway? There's no official definition, but Americans and their leaders seem to know it when they see it.

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.”

The traditional political focus on the middle class comes as fewer people feel like they’re still part of it. A Pew Research Center report  this year found that 49 percent of people define themselves as middle class, down from 53 percent from four years ago.

“Statistically, that’s a significant shift, but beyond statistics it feels right,” said Rich Morin, a senior editor with Pew Research Center. “It’s been a tough four years.”

In fact, Morin said, Americans’ sense of how the middle part of the economic spectrum is doing is surprisingly accurate. The polling data on whether Americans feel like they are still part of the middle class matches well with the researchers’ economic data on median income in the United States, which has fallen in recent years after adjusting for inflation.

Still, experts say the term middle class has a cultural connotation that goes beyond the number on your paycheck or tax stub.

Kevin Leicht, director of the Iowa Social Science Research Center at the University of Iowa, said many Americans think of a middle-class life as being one in which you have a stable job, own your own home and occasionally buy something substantial like a new car. You also either went to college or have the aspiration of sending your children to college.

Beyond that, he said, the term middle class invokes the type of person who gets married and has kids, pays their bills on time, doesn’t get in trouble with the law and maybe goes to church.

“In the United States, it’s probably more of a cultural category than an economic one,” he said.

He thinks Americans’ affinity for the middle class also comes partly from a natural suspicion for both the richest and the poorest Americans. Audacious wealth has traditionally been frowned upon in this country, he said, while there’s also often a fear-based bias against people who are poor.

“Because a lot of us are two missed paychecks away from being in exactly the same position, we have to act like there’s something systematically wrong with people who are in that position,” Leicht said.

The sense of a shrinking middle class also comes amid evidence that the rich are getting richer and the poor are getting poorer, discouraging many Americans.

“They are aware that economic inequality is growing. And a majority – a substantial majority – say it’s a bad thing,” Morin said. “Everyone aspires to be upper class, but people are aware that as more Americans move up into the upper class, more Americans are moving down, and that’s not a good thing.”

The big question now is whether Americans’ discouraged attitudes about the middle class will change if the economic recovery starts to pick up.

In general, experts say that history would show that Americans will grow more optimistic about the middle class, and the American dream, as economic conditions improve. But, they note, this recession and weak recovery has been different from any other we’ve experienced in recent decades, and the future remains uncertain.

“I’m sure a strong recovery would help, but that’s a ways off,” Smeeding said. “Our standard of living is lower now than it was in 2006.”

Readers, how do you define a middle class life and do you think you are living it? Send me an e-mail, including contact information, and and we’ll use some of your responses in an upcoming story.

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