There've been, by our very rough count, something like a zillion sound bites through the course of this campaign and we've still got a month and a half to go. The candidates have been talking about anything and everything they think will resonate with voters, including heavy use of a phrase that might affect the broadest chunk of Americans:

"The middle class."

So, um, who exactly is that?  There's no government definition. Economists generally agree it's households who earn about $40-120,000 a year. But that's a big range, and that's just the numbers.  

When you close your eyes and picture a typical middle class American, what do you see?

We went out on the streets of cities across the country to ask people to define middle class, and no matter where we went, they agreed on a lot of the basics.

You need a decent job. You own a home... maybe a barbecue in the backyard. 

But start filling in the details, and things get tricky.  Like, that decent job? What qualifies as decent? People gave answers that ranged from white-collar to blue-collar. Doctor. Lawyer. Police. Firefighter. Teacher. Skilled trades. Autoworker.

As far as education, also a huge range. Some said you need a high school diploma. Others, a college degree.  

People disagreed on even just the basic philosophy of what it means to be middle class.  As Marvelous Baker, a foundation administrator who lives in Cleveland, sees it, middle class means “the ability to provide the necessities of life.” But office worker Emmeline Ross of Los Angeles says a middle class family should be “able to buy things not because they need to, but because they want to.”

If you’re confused, that’s because the definition of the middle class is confusing.  Especially right now.  “It's like middle class is disappearing,” said Robin Brown, a retired custodial worker in Cleveland.  Ross, the office worker in Los Angeles, felt the middle class just is “not what it used to be.”

What about you? Do you consider yourself middle class? And does that mean you have a backyard with a barbeque? We're looking for the view from your middle-class window. Submit your photos -- and stories -- at "Picture This: The Middle Class."

Great Moments in Middle Class History

So, what did the middle class used to be? 

One of the first references to the middle class made by an American was in 1792, when Thomas Paine wrote:

"A poll tax was levied. It excited, as it naturally must, universal detestation among the poor and middle classes."

Yes, even then the middle class stereotype was someone annoyed by taxes, but that’s where the similarities end. Because the middle class Paine was talking about wasn’t white collar, or blue collar. It was... the yeoman farmer.

Once upon a time, according to writer Michael Lind, author of Land of Promise: An Economic History of the United States, our founding fathers realized that if they were going to actually make their crazy idea of a democracy work, they needed “a dominant middle class," who, because of a certain amount of economic security and economic independence is "capable playing various roles that society in a republic demands, whether as a voter or as a juror.”

Since there were a lot of farmers running around back then, they seemed like good candidates for the job. But, Lind argues, farmers didn't just naturally become economically independent and secure. America's first middle class didn't just happen. 

It was “an artificial creation of private sector and public sector policies," Lind argues, including "distribution of federal land to farmers through the Homestead Act, and elementary public education.”

Things that America invented to help support this new middle class, says Lind. Of course, by the early 1900s, new technology meant we needed fewer farmers. The rest headed to factories in cities, where conditions were poor, and they didn't get paid much.

America looked at its dissolving middle class, and started, in modern parlance, to freak out.

“Thinkers at the time, on the left and the right and the center, all said ‘we have to do something,'” says Lind.  They feared that “a desperate, low-wage majority that lacked property, that lacked any stake in society, would turn to demagogues.” The theory back then, Lind argues, was “a stable democracy requires a dominant middle class.”

It took almost 30 years for the U.S. to figure out how to bring its new factory worker majority in to the middle class.  Franklin Roosevelt was still grappling with task when he was president.  Lind says that eventually, due largely to public and private policies created during the New Deal and after World War II including Social Security, government-backed mortgages, the GI bill, and a suite of labor laws pushed by unions, a new version of the middle class was born.  It was mostly made up of workers in the manufacturing sector. 

Fast forward to today, when new technology and a changing global economy mean we need fewer factory workers in the U.S.  It’s a very similar moment, Lind argues, to that one 100 years ago when we were shifting off the farms. We’ve got a void where the bulk of the middle class used to be and we haven't quite figured out how to fill it.

Both presidential candidates have hinted at their visions for the future of the middle class this election year. For President Barack Obama, education is key.

“Education was the gateway to opportunity for me,” he told the crowd at the Democratic National Convention speech in Charlotte recently. "And now, more than ever, it is the gateway to a middle class life.”

For Republican presidential nominee Mitt Romney, the gateway is through small business.  In his acceptance speech at the GOP convention, he said to a cheering audience, “We will champion small businesses, America's engine of job growth. That means reducing taxes on business, not raising them.” 

Both visions -- of education and entrepreneurialism -- can be inspiring, says Lind. The problem, he argues, is “the math simply does not work.” 

And he means the math on both sides. On the one hand, only about 10 percent of Americans are self-employed. On the other hand,  70 percent don’t have college degrees. So, the bulk of Americans won't be owning small businesses or becoming white collar professionals with B.A.s anytime soon.

Lind says -- and most economists agree -- that for the foreseeable future, most of America’s jobs will be “personal service jobs.”  Everything from elder care to child care to janitors to restaurant servers. Jobs that can’t be off-shored or automated.   

“The question is, will this be a huge population of the working poor as you have in many Latin American countries?” Lind asks.  “Or will we take the social reforms necessary to turn a service sector majority in to a middle class majority?”     

If we’re really worried about the future of the middle class in this election, Lind says, that’s the question we should be trying to answer.