Washington ? Already advertising at record levels, Barack Obama has scheduled a half-hour commercial for prime time on Oct. 29, the anniversary of Black Tuesday in 1929 and six days before Election Day.

Obama campaign officials said the campaign had secured a 30-minute block of time at 7 p.m. on CBS and NBC. CBS already was juggling its lineup to accommodate the Democratic presidential candidate, moving back an episode of “The New Adventures of Old Christine.”

Such a vast purchase of commercial time is a multimillion-dollar expense, but Obama has been spending dramatically on ads, overshadowing rival John McCain and the Republican National Committee.

Short political spots have been the traditional way for politicians to communicate with voters. But a prime-time, sitcom-length commercial would provide Obama an opportunity to make a closing argument to the entire country.

“It’s a luxury to be able to afford that kind of communication,” said Tad Devine, a Democratic media consultant who was a senior adviser to John Kerry’s 2004 presidential campaign.

That Obama has the ability to buy such a huge block of prime time is a testament to his prodigious fundraising. He has not been shy about spending it.

On Monday, for instance, he spent $3.3 million in a single day of TV advertising. At that rate he will spend more than $90 million on ads through Election Day – more than all the money Republican rival John McCain has to spend on his entire fall campaign.

McCain’s ad spending Monday totaled about $900,000 and the Republican National Committee weighed in with about $700,000 worth.

All whopping numbers, but the disparity between Obama and the Republicans is so wide that it has allowed Obama to spend in more states than McCain, to appear more frequently in key markets and to diversify his message by both attacking McCain and promoting his own personal story.

“Money doesn’t always mean victory, but it means that you have more options to cover more of the battlefield,” Republican strategist Terry Holt said. “We’re going to have to win with less.”