President Obama's post-convention "bounce" in national polls may result mainly from an onslaught of pro-Obama TV ads rather than the spectacle and message of the party convention itself, according to a new analysis of media tracking data by the independent Wesleyan Media Project at Wesleyan University.

The president's campaign and affiliated groups dominated the airwaves in the past two weeks, eclipsing rival Mitt Romney and his affiliated groups in total number of ads running by a two-to-one margin, Wesleyan found, using data from CMAG/Kantar Media.

Between Aug. 26 and Sept. 8, Obama aired nearly 40,000 spots on broadcast and national cable TV compared with 18,000 for during the same period.

"During both the Democratic and Republican conventions, pro-Obama advertisers 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," said Erika Franklin Fowler, co-director of the Wesleyan Media Project.

Over the entire general election race, starting in late April when Romney clinched the Republican nomination, the number of ads aired by both sides has been relatively equal, the group found.

Since the conclusion of the Democratic National Convention on Sept. 6, national polls have shown Obama widening a lead against Romney.

Gallup's national tracking survey released today, using a 7-day rolling average, gives Obama a seven-point lead over his GOP rival, 50 to 43 percent. The margin of error is plus or minus two points.

The latest ABC News/Washington Post poll , released Tuesday, showed a similar dynamic, with Obama opening up a 50 to 44 percent lead among registered voters. That compares with a 46 to 47 percent Obama-Romney contest immediately before the conventions.