BARACK Obama will become the first presidential candidate in 16 years to air a 30-minute primetime infomercial on US TV networks tonight.
The rare and expensive move, thought to have cost his campaign about 1.9 million, will even cause the baseball World Series final to be delayed by 15 minutes so NBC, CBS, and Fox can air the spot simultaneously.
Mr Obama will highlight his "closing argument" in the infomercial, which underscores his campaign's financial dominance over Republican rival John McCain with less than a week left in the race for the White House.
Mr McCain, who trails in national polls, mocked the move on the campaign trail yesterday, saying: "No one will delay the World Series game with an infomercial when I'm president."
ABC will be the only major US network not to run Mr Obama's message at 8pm ET (midnight tonight GMT), preventing a so-called "roadblock" on the broadcast networks.
Neither network officials nor Obama campaign aides would discuss the cost of the television time, but estimates by the Associated Press put it at around three million US dollars (1.9m). CNN suggested it could reach the five million dollar mark (3.1m).
The estimates are less than the US TV networks would otherwise get for the 10 or 11 advert "units" they run during that half-hour, but Mr Obama will be charged the "lowest unit cost", in compliance with federal law.
The Obama campaign, which rose in the polls due to Mr McCain's mishandling of the economic crisis, is running the infomercial on the 79th anniversary of Black Tuesday, the start of the Great Depression.
Mr Obama is following in the steps of John F Kennedy, who presented a half-hour commercial that featured parts of his speech in Houston about his religion, and Richard M Nixon, who bought two hours of time on the eve of the 1968 election at a cost of 400,000 dollars (251,000).
The last candidate to use the format was Ross Perot, in 1992, when he detailed his plan to cut the deficit before an audience of 16.5 million people.
As the 2008 election nears its climax, Mr Obama will also hold his first joint rally with popular former President Bill Clinton in the critical state of Florida.
Mr Clinton gave the 47-year-old Illinois senator a rousing endorsement at the Democratic Party's national convention in August, but the two men often antagonised one another during the prolonged and frequently-bitter primary battle between Mr Obama and Mr Clinton's wife Hillary.
It will be the first time they have appeared together and Orlando sits in an important swing part of the Sunshine State, where Mr Clinton could help Mr Obama win votes among the white working-class voters who strongly supported his wife.
Mr Obama is also using his record levels of fundraising and grassroots organisation to take the fight to Mr McCain on traditionally-Republican turf.
Florida, Ohio, Virginia, Indiana, North Carolina, Nevada, Missouri and Colorado are all key battlegrounds this year, all voted for Republican President George Bush in 2004, and Mr Obama leads in the latest polls in all 11 of these states.
Newt Gingrich, the former Republican house speaker, told the New York Times: "Any serious Republican has to ask, 'How did we get into this mess?'
"It's not where we should be, and it's not where we had to be. This was not bad luck."
In Florida, which offers 27 of the 270 electoral college votes needed to win the presidency, the Obama campaign is making a vigorous push after becoming convinced they can win the state following two days of rallies there last week.
The Democrat can afford to compete in several key states simultaneously as he has repeatedly broken fundraising records, bringing in 150 million dollars (96.2 million) last month, more than double the record he set a month before.
And he opted out of public funding so is free to spend whatever he can raise in a bid to get elected, while Mr McCain is restricted to spending no more than 84.1 million dollars (53.9 million) between his party's national convention and the election next Tuesday.
The Obama campaign's extensive grassroots organisation and a get-out-the-vote drive has also turned what was about a 250,000-voter registration edge into a 650,000 advantage in Florida alone.