Democratic presidential candidate Barack Obama plans to air a 30-minute commercial during prime time on Oct. 29, six days before Election Day.
Obama spokesman Bill Burton said the campaign has secured the time from CBS and is negotiating with other networks to air the half-hour spot.
Obama has been outspending rival John McCain in advertising and has been airing commercials of up to two-minutes in length.
Ross Perot famously aired a 30-minute ad during his independent presidential campaign in 1992, attracting 16.5 million viewers.
Short political spots have been the traditional way for politicians to communicate with voters. For Obama, however, a longer piece would be a dramatic way to close his argument to voters.