Hillary Clinton has vowed, many, many, times, not to "raise taxes on the middle class." The middle class, she'll argue, must be protected, encouraged, nurtured, and grown. That's super, but if you ask her to define the middle class, things tend not to go so well. In fact, it appears she doesn't really know what she thinks the middle class actually is.
Take a look at what happened when a reporter asked her for a concrete definition of Hillary's favorite voting bloc: