One of the early peculiarities of the advertising campaign is the half-hearted effort in Pennsylvania—a state which figured prominently in the electoral calculus of the last three presidential elections. Despite that place in recent electoral history, Romney hasn’t aired any ads in Pennsylvania since the general election began. And although the Obama campaign and the super PACs have waged a low-intensity ad war in Pennsylvania, the most recent data suggests that even these limited efforts might be winding down.

For the first time in the campaign, Republicans are completely off the air in Pennsylvania. According to The Washington Post’s ad tracker, neither Crossroads nor Restore Our Future have aired ads in Pennsylvania since the beginning of July, and although Americans for Prosperity purchased buys for the early half of July, they appear to have gone off the air as well. This could be temporary, of course: there were weeks when the GOP went off the air in Michigan, only to return a few weeks later. Americans for Prosperity isn’t airing any ads this week, and they were carrying the load in Pennsylvania before dropping off the air, so they might start contesting Pennsylvania again once they return to the presidential race. But the decision to cease advertisements shouldn't be overlooked: ads quickly lose their punch once the airwaves go quiet, so it's important to remain persistent once advertisements begin.

Why is Pennsylvania falling off of the radar? Although the state is typically characterized as a white working class state reminiscent of the Midwest, the Democratic coalition in Pennsylvania is far more diverse and upscale than Ohio or Michigan. Democrats also have a large registration advantage in Pennsylvania, and a Romney victory would require a degree of crossover appeal that he has not yet demonstrated. Instead, Romney and his allies appear more interested in testing the waters of the Great Lakes, where demographics or electoral history are arguably more promising than Pennsylvania. Obama is more dependent on white working class voters in Michigan than Pennsylvania, and recent polls provide cause for Republicans to be hopeful about their chances. This week, Crossroads turned up the volume in Michigan and spent nearly $600,000 on advertisements. That’s not as much as other battleground states, but it’s a hefty investment. For comparison, Obama spent $1 million in Ohio—a slightly larger state, generally considered more likely to decide the election. The RNC has also announced it will invest in Wisconsin, a state where Obama looks strong but that Kerry won by just 14,000 votes in 2004.

Perhaps as a result of the diminished GOP effort, the Obama campaign has slashed their Pennsylvania spending in half to just $173,000 last week—or about as much as their spending in the Raleigh media market and less than any other state. Priorities USA, the Obama-aligned Super PAC dedicated to attacking Bain Capital, continues to air advertisements at their earlier pace—which is somewhat surprising given their limited resources. But oddly, the Obama campaign hasn't aired ads in either Michigan or Wisconsin since the general election started, even while they continue to defend Pennsylvania. Clearly, the Obama campaign believes they're more vulnerable in Pennsylvania, which could be more of a testament to their confidence in Michigan or Wisconsin—two states they won by more than 16 points—than dire weakness in the Keystone State.

While Obama could certainly lose Pennsylvania if he loses nationally, polls, demographics, and electoral history suggest that the state will tilt Democratic in a close election. Although Obama seems to consider Pennsylvania their weakest blue state, the GOP's decision to suspend advertisements in the state, even if temporarily, is a telling indication of where Pennsylvania fits into Romney’s path to victory.