With fewer than three weeks before the presidential election, both sides have ramped up their advertising to an incredible extent. Over the last three weeks, the Obama campaign has purchased $40 million in swing state ad time, while the Romney campaign has spent $49 million. Overall, the Obama campaign is outspending its competitor, $300 million to $164 million. That said, the advantage shifts when you factor in outside groups: total spending from Team Romney — the campaign and Republican Super PACs — comes to $455 million. By contrast, total spending from Team Obama is $352 million.

But the fact that Republicans are outspending Democrats hasn’t translated to actual ad saturation. By the end of last week, Obama and his allies had aired about 5,000 more ads than their Republican counterparts. Indeed, despite speculation that Team Obama was on the verge of conceding states like Virginia, Florida and North Carolina, the bulk of the campaign’s ad spending remains located in two of those states — two of the top six media markets for the Obama campaign are located in Virginia (the Hampton Roads area) and Florida (the Tampa area).

To go back to a point I made several weeks ago, this has everything to do with who controls campaign cash, as well as the actual logistics of buying and scheduling ads. Obama is far less dependent on outside spending than Romney, which — because of campaign finance law — means he pays lower rates than the outside groups that direct the bulk of Romney’s spending. When you combine that with earlier — and thus cheaper — ad buys from the Obama campaign (for instance, they made a $77 million buy in August for the fall), the result is that the Obama camp is airing a greater volume of ads despite the fact that they’re being outspent.

In other words, there’s still a real chance that Obama will out-advertise Romney in the final two weeks of the campaign — which is when ad spending has its greatest effect on the electorate. In which case — if they’re leading — Team Romney has to hope that they’ve built up enough of an advantage to withstand the onslaught. And Romney may not be leading. After a week of excellent polling, Obama has begun to reestablish the slight lead he’s held for most of the year: Of the eight national polls published in the last 24 hours, six show an Obama lead, one shows a tie, and the other, from Gallup, shows a 7 point Romney lead.

If this trend holds, then Obama’s ad advantage might be the thing that helps seal the deal.

Jamelle Bouie is a staff writer at The American Prospect , where he writes a blog .