At yesterday’s townhall meeting at Great Valley High School in Malvern, Pennsylvania, Obama received his strongest applause while discussing three subjects. Obviously, the audience was enthusiastic about education (better pay for teachers, and more affordable college tuition). They literally went nuts when Obama talked about providing everyone with access to the same quality health care coverage enjoyed by members of Congress. But the biggest applause line was about ending the occupation of Iraq. Even I was surprised by the thunderously approving response. Nick Timiraos of the Wall Street Journal has a partial explanation.

With Pennsylvania’s manufacturing and steel towns financially distressed, the economy has been the top focus for both candidates across the state, but Philadelphia’s suburban counties remain better off than the rest of the state.

That means the Iraq war could be of greater importance in the suburbs than it is elsewhere. In 2006, a strong current of opposition to the Bush administration in the suburbs flipped two congressional districts to Democratic control. Voters elected Rep. Patrick Murphy, the only Iraq war veteran serving in Congress, and Rep. Joe Sestak, the highest-ranking former military officer ever to serve in Congress.

Chester County, Pennsylvania is an almost embarrassingly affluent place, and the Great Valley School District is even more so. Sometimes it seems like everyone lives in a massive house and drives a massive car, although that’s not really true. But, it’s wealthy. And I suspect that almost no one that was in the audience has a brother or daughter serving in Iraq. When Obama said that gas prices were killing people, someone yelled back, “Killing people!!,” and the crowd murmured in agreement. I had to laugh because higher gas prices were merely inconveniencing that crowd. They’d have to go down to Philadelphia or up to the Lehigh Valley to see people actually getting murdered by the sluggish economy. And, in any case, a look at the parking lot proved that the people of Great Valley have not yet traded in their behemoths for hybrids. People here are ‘feeling the pinch’ but they are not yet losing their homes or downgrading their vehicles. Perhaps they have canceled they gym memberships and stopped eating out three times a week.

But all of this made their reaction to the war all the more surprising. Could it be that their relative affluence gives them the luxury to worry about the welfare of others? Or could it be that their education enables them to tie the threads together and see that wasting resources in Iraq ultimately is tied to lower education budgets, fewer grants, and more expensive college tuition?

Is there a different intersection of perceived self-interest in this crowd than in the depressed steel-mill towns to the north? I don’t know. What I do know is that the war is now incredibly unpopular in the Philly suburbs. And it’s driving voters to the polls.

Of the state’s more than 300,000 new Democratic voters this year, nearly 45% come from Philadelphia and its four suburban counties, which account for about one-quarter of the state’s 12 million residents.

The result of the Pennsylvania primary is going to pivot on turnout. If the Philly suburbs turnout at a higher rate than the rest of the state (and there is reason to believe they will), Obama will win an upset. It’s also going to be important to see if there is differential motivation in the camps of the two candidates. Right now, it seems like Obama has a lot more support but, more importantly, it seems like Clinton supporters are lying low…almost afraid to openly profess their preference. Whether they’ll be as motivated to turn out to vote as Obama’s supporters is an open question. Based on my experience in Malvern yesterday, I’d have to say that Obama’s credibility on opposing the war is the main reason why he is doing so well here.