With Election Day less than a week away, Barack Obama has tried to reinforce his lead in the polls by purchasing primetime advertising spots on national television networks. Last night, the Obama ads aired during the 8:00-8:30 p.m. time slot on three of the four major networks—CBS, NBC, and FOX—and cable’s BET. Each ad cost the Obama campaign roughly $1 million.

That sounds like a hefty price, but it actually represents a discounted rate. All major commercial television stations are legally obligated to provide federal candidates with the opportunity to purchase airtime from all “classes and dayparts” of the channel (with the exception of previously scheduled news time) at the “lowest unit rate,” or the reduced rate that is typically available only to the best advertising customers who buy in bulk. The caveat is that these ads must air within 45 days of a primary election and within 60 days of a general election. In the 2008 presidential campaign, the special rates became available to candidates starting on September 5.

The 30-minute Obama ads are not without precedent. The last time a presidential candidate bought this much continuous airtime was in October 1992, when Ross Perot paid $380,000 to purchase 30 minutes on CBS. During his half-hour block, Perot used charts and other visual aids to make his case. Forty years earlier, vice presidential candidate Richard Nixon went on the air to deliver his famous “Checkers” speech, in which he rebutted charges that he had accepted illegal gifts.

Obama could spend $250 million on advertising by the end of the campaign.

Under FCC broadcasting guidelines, commercial stations are required to grant federal candidates “reasonable access” to TV advertising. The individual channels decide the timing and length of the ad spots they sell, but they are expected to work with each candidate to accommodate his or her needs.

The Obama campaign negotiated for highly coveted airtime. FOX, which aired the World Series, worked with Major League Baseball to postpone the start of last night’s Phillies-Rays game by 14 minutes. The network released a statement saying it “would be willing to make similar time available to Senator McCain’s campaign.”

But could McCain afford the airtime? Probably not. “It’s a luxury to be able to afford that kind of communication,” media consultant Tad Devine, who advised John Kerry’s 2004 presidential campaign, told the Associated Press. Unlike Obama, McCain accepted public financing for his general election campaign, which means he cannot fundraise privately and is limited to $84.1 million in overall expenditures. According to the Campaign Media Analysis Group (CMAG), McCain has been outspent in TV ad purchases by a margin of 4 to 1.

Indeed, Obama’s extremely successful private fundraising push—which raised $150 million in September alone—has given him a huge advertising edge. CMAG president Evan Tracey believes that Obama could spend $250 million on advertising by the end of the campaign. As Election Day draws near, that’s just one of the big obstacles that McCain must overcome.

Alexis Hamilton is assistant editor of THE AMERICAN. Jessica Leval is a research assistant at the American Enterprise Institute.

Image by Darren Wamboldt/The Bergman Group.