Scott Brown and national Republicans have spent a great deal of time lately describing Elizabeth Warren as an elitist. In a steady stream of press releases and statements, they have regularly referred to her in sneering tones as “Harvard professor Elizabeth Warren,” which they seem convinced will be viewed by Massachusetts voters as a negative.

That’s the context for this new ad the Warren campaign released today. Warren reminds voters that she grew up in modest circumstances and points to higher education’s role in helping her get ahead. She also tries to appropriate the issue of student loans as her own:

The ad underscores the degree to which both sides view Warren’s biography and character — and voter perceptions of it — as central to the campaign’s outcome. But Warren’s ad is about more than reminding voters that her upbringing was anything but “elitist.” It’s also about pivoting off her life story to reframe the race’s central argument over government and taxation as one about fiscal values and priorities.

As I noted here the other day, one of the key dynamics in the race is that voters have already accepted that Brown is likeable and independent — but a huge bloc reamins undecided anyway. The race will turn heavily on whether Warren can clear a basic likeability threshold — which is why Brown’s allies have spent months attacking her as an elitist in order to drive up her negatives. The attacks on Warren’s character are aimed at the 800,000 or so voters who didn’t come out during Brown’s 2010 special election but will come out in a presidential year, many of whom may be Obama supporters.

The “elitist” attack has been everywhere. Most recently, Brown and Republicans have rolled out the silly argument that Warren’s failure to voluntarily pay higher taxes on her own proves she’s an elitist hypocrite, given her call for higher taxes on the wealthy.

The new Warren ad suggests Dems see the issue of student loans as a good way to reframe the argument over taxes and the need for more goverment investment in the future. Indeed, Obama himself is launching a campaign on this front, too. In the spot, Warren showcases herself as an example of what education can do to create opportunity for those struggling to hang on to the middle class, and adds:

Today, Washington lets big corporations like GE pay nothing. Zero in taxes. While kids are left drowning in debt to get an education. This isn’t about economics. It’s about our values.

Republicans are spinning Warren as a pointy-headed Harvard professor who thinks she knows how to spend ordinary folks’ money better than they do. Warren wants voters to get to know a maintenance man’s daughter who made good through education and hard work, and as a result knows how urgently we need to take action to shore up and sustain the middle class. The question of which Warren undecideds accept could decide the race.