By Barbara Raab, Senior Producer, NBC News

What does it mean to be part of America’s middle class? And who is middle class? A new poll asked Americans to define what it means to be part of the middle class, and to put themselves somewhere along the spectrum between upper-, upper-middle, middle-, lower-middle- and lower-class.

Here are some of the key findings:

46 percent of Americans consider themselves solidly middle class. But it’s not necessarily a source of comfort. As the pollsters put it, “the American middle class is anxious and in flux. While many dream of upward mobility, most are concerned about falling out of their economic class” over the next few years.

While half of all Americans consider higher education to be the most effective way to protect and earn middle class standing, many middle class Americans are struggling with how to pay for the high cost of that education.

Perhaps most noteworthy is what might be called the downsizing of the American dream. Traditionally, that dream included upward financial and professional mobility, buying a home, yearly vacations and saving for the future. Now, the poll found, a solid majority (54 percent) of Americans believe that being middle class these days means keeping up with expenses and holding a steady job, not falling behind or taking on too much debt.

High anxiety, in plain sight.