The Obama and Romney campaigns have shattered records for spending on political ads in this year's presidential campaign, a Wesleyan Media Project study confirms. And both sides are unloading a massive final wave of TV, radio, and internet ads targeting voters in the handful of swing states expected to decide what is looking like one of the closest battles for the White House in history. Just how much money are President Obama and Mitt Romney spending? Here, a look at this year's political ad blitz, by the numbers:

$900 million
Amount spent on ads from June 1 to Oct. 21, including from super PACs

$600 million
Spending on ads at the same point during the 2008 campaign

Total ads aired by the Romney and Obama campaigns

Ads aired by the rival presidential campaigns during the same period in 2008

Ads aired by the campaigns in the same interval in 2004

Percent increase in the number of ads in 2012 compared to the same time period in 2008

Pro-Obama ads during the first three weeks of October

Pro-Romney ads during the first three weeks of October

$87 million
Amount Republicans, including the campaign, party, and their supporters, spent on ads during that time period. In 2008 they only spent $40 million in the same period.

$77 million
Amount the Democratic side spent on ads during that time period. In 2008, Democrats spent even more — about $86 million.

Percent increase in spending on TV ads by Democratic-leaning groups outside the official campaign and party

Percent increase in ad buys by Republican-leaning groups

$47 million
Cost of advertising paid for by those GOP groups over the past three weeks

$12 million
Amount spent by their Democratic counterparts over that same period

Number of the nation's top 15 media markets in which pro-Obama ads, by the campaign and its supporters, have outnumbered those aired by Romney and his backers. The only markets where pro-Romney ads dominated were Columbus, Ohio, and Norfolk, Va.

$1 billion
Amount the campaigns are expected to have spent on the million or more ads they will have aired by the time Election Day finally arrives. "When all is said and done," says Erika Franklin Fowler, co-director of the Wesleyan Media Project, "2012 will go down as a record pulverizing year for political advertising."

Sources: The Daily Beast, UPI, The Washington Post, Wesleyan Media Project

Read more political coverage at The Week's 2012 Election Center.