1. People mean the actual federal budget deficit, but are misinformed (Krugman/Drum).
2. People mean the federal debt, not the budget deficit, and correctly believe that the debt is still rising (suggested by Megan McArdle today and by several of us after Eric Cantor said the deficit was going up recently; this was if I recall correctly a big Mario Cuomo talking point in the 1980s -- if only Democrats would say "debt" instead of "deficit," they would win all the elections, or something like that).
3. People mean "economic bad times," not the federal budget deficit. Recall the voter who asked George H.W. Bush, Bill Clinton, and some kook who security had accidentally let on stage during a presidential debate about how the
4. People mean "stuff I don't like in the budget," not the federal budget deficit. Goes with what I call the GOP war on budgeting -- for example, if that's what you mean by "deficit," then of course the ACA increases the deficit regardless of what CBO says.
I'm confident that it's roughly split between explanations 4 and 3, but I don't really have any hard evidence for it, and all of them are plausible. I've asked before, but: Hey, pollsters! Help us out here! I'm not really sure how to go about testing this one...surely not simply posing these four possibilities. But it sure would be nice to have an idea about what people actually mean when they talk about the deficit.
*Corrected. I remembered this wrong; thanks to Drezner for the catch. Don't think it changes the point, though.