Maybe, says Erika Franklin:
During both the Democratic and Republican conventions, ads favoring Obama dominated the airwaves in numerous markets, including key swing states such as Colorado, Ohio, Nevada, and Virginia. This advantage may help to explain why Obama’s ‘convention bounce’ was larger than Romney’s.
John Sides, who created the above chart, is intrigued:
What makes this hypothesis plausible is that imbalances in advertising spending are often necessary for advertising to influence the polls. If the candidates are at parity, then the two sides’ spending may simply cancel each other out. And, as some new research suggests, these imbalances may be more prevalent in presidential campaigns than previously thought. Certainly a lack of complete parity has been the norm in each of the past several months.
But Obama supporters should not get too excited. The effects of ads also decay quickly. Any advantage over these past several months, or even these past two weeks, should be less important than an advantage in late October.