President Obama and his allies have aired more ads in battleground states this month than Mitt Romney and his supporters, despite being outspent by the Republican nominee and GOP groups, according to a study released Wednesday.

The Obama campaign and its supporters spent $77 million on 112,730 advertisements from Oct. 1 to Oct. 21, according to the Wesleyan Media Project, which tracks and analyzes political ad spending. Romney and his allies, by contrast, spent more money — $87 million — on 15,000 fewer spots than their opponents.

The study also confirmed that 2012 has already shattered previous records for presidential ad spending, with 915,000 ads aired during the general election campaign through Sunday — a 44.5 percent increase compared with the same period four years ago.

The findings suggest that Obama and the Democrats may be able to weather a storm of Republican advertising purchases aimed at knocking the incumbent off balance in the final weeks of the election. One Republican media buyer calculates that GOP groups are outspending Democrats in this week by nearly 2 to 1.

But Obama has a key advantage over Romney by raising the bulk of his money through his campaign committee, which qualifies for discounted ad rates under federal election laws. That can allow Obama to pay much less for the same ads compared with conservative super PACs and other outside groups, which don’t qualify for such rates. 

MAD MONEY | Presidential ad spending doubles in swing states

Romney has less money under his direct control because he relies more heavily on wealthy donors who give to the Republican Party and on ad spending by well-funded independent groups. Unlike Obama, Romney also bought relatively little ad time in advance — which is cheaper — and has tended to choose more expensive ad spots with guaranteed placements.

“There was a lot of talk that Romney and his allies were hoarding resources for a major ad push in the closing moments of the campaign,” Michael Franz, co-director of the project, said in a statement. “We just haven’t seen that to date on local broadcast. And time is running out.”

Erika Franklin Fowler, the other Wesleyan co-director, noted that while the volume of campaign advertising in 2012 has exploded, it is directed at a much smaller number of swing states than 2008. Las Vegas, Denver and Cleveland have been at the epicenter of presidential ad volume this year, the study found, while markets in 2008 battlegrounds such as Missouri and Indiana have dropped off the map.

Obama maintained an advantage in total ad volume in 13 of the top 15 markets during the first three weeks of October, the study found. Romney was ahead only in Columbus, Ohio, and Norfolk, Va., and even there only slightly.

Romney also relies much more heavily on assistance from groups such as American Crossroads and Restore Our Future, which accounted for nearly half of the pro-Romney ads aired this month.

The Obama campaign ran 86 percent of the spots aired on the president’s behalf. The reelection campaign has aired a total of 461,000 commercials overall — more than the Romney campaign and all the Republican groups that are helping him combined.