We’ve written quite a bit about the rhetorical attention President Obama — and Democrats more generally — are paying to middle class voters of late.

White House Press Secretary Jay Carney speaks during the daily briefing after U.S. President Barack Obama delivered a statement urging Republicans in Congress to join Democrats to ensure taxes don't go up on middle class families in the Brady Briefing Room of the White House on December 5, 2011 in Washington, DC. (Photo by Alex Wong/Getty Images)

In the new NBC-Wall Street Journal national poll, respondents were asked which party would do a better job of “looking out for the middle class”. Forty four percent named Democrats while 24 percent opted for Republicans. Seventeen percent said neither party was looking out for the middle class and 12 said both were doing so about equally.

As interesting as Democrats’ current edge on the question is the steadiness of the party’s advantage over time. In an October 1996 NBC-WSJ survey, Democrats enjoyed an identical 20-point margin over Republicans. Ditto an October 1993 NBC-WSJ poll. Go all the way back to November 1989 — when a teenage Fix was rocking a Chicago Bulls Starter jacket and listening to “3 Feet High and Rising” — and Democrats had a similar 23-point edge on the “looking out for the middle class” question.

What does the persistence of Democrats’ lead on the middle-class question tell us heading into 2012?

That when they are talking about the middle class (and rising inequality more generally), Democrats are playing the equivalent of a home game with voters. That is, voters have a lasting image of Democrats as the party looking out more for the middle class. Therefore when the two parties fight over who is truly fighting for the vast middle, it’s more likely that the Democratic argument wins out. (It’s like a Duke hoops player getting a charge call at Cameron Indoor Stadium. It just always happen.)

Republicans have a home field advantage, typically, on issues like national security and taxes. In the NBC-WSJ poll, Republicans are favored by two points over Democrats on which party deals better with the economy and have a 13-point edge on dealing with terrorism.

Given how large a proportion middle-class voters are likely to be in the 2012 electorate — much more (and a chart!) on that here — winning them is central to both party’s winning math.

The NBC-WSJ numbers suggest Democrats would do well to continue to push the inequality argument and use it as a wedge to cast themselves as the true defenders of the middle class.

How do Republicans turn the economic debate into a home game for their side? Focus on the federal debt. In the NBC-WSJ numbers they are favored by 11 points over Democrats on the issue.

Much of elections — or at least winning elections — is about making sure the playing field on which the races are fought favors your side. So will the economic argument in the 2012 election be centered on inequality or the growing national debt? Answer that and we’ll tell you who will win.