And at least as of the end of August, the Obama campaign was left with $89 million cash in the bank to Romney's $50 million.
Obama has also been more strategic about where his campaign spends his money -- sometimes aiming for programs that are cheaper, like the ones that air during the day -- in order to target specific demographics, Fowler said.
"The campaign is being incredibly efficient in the way they've gone about spending on ads," Fowler said. "Even within markets you're seeing some of the targeting in the program where the campaign is spending a large amount of their dollars."
The "micro targeting" of television ads that the Obama campaign utilizes aggressively is actually a strategy that Republicans pioneered in previous elections. But the Romney campaign has been slow to utilize it so far in this election.
"One of the puzzling things is why Romney's campaign isn't using it more frequently," Fowler said.