"Barack Obama is going primetime in a big way.

In a break with recent campaign ad tradition, Obama's campaign said it has purchased a half-hour of airtime on CBS and NBC for a primetime political infomercial on Oct. 29. Obama's campaign is also reportedly looking to make similar half-hour buys on other broadcast networks.

The network buys -- which could cost the Obama campaign around $2 million each -- demonstrate Obama's massive fundraising advantage over his Republican rival, Sen. John McCain. Obama has been outspending McCain by a wide margin, sometimes by as much as 3-to-1, in almost all of the 14 states where the election is still considered competitive.

Coming just six days before the election, Obama's primetime ad may put pressure on McCain to respond with a similar national message, said Darrell West, a Brookings Institution scholar who is the author of "Air Wars: Television Advertising in Election Campaigns 1952-2004."

However, McCain's resources are limited; he agreed to accept federal matching funds that limit his campaign to $84 million in September and October. Although McCain is getting a boost from the Republican National Committee, his campaign has already stopped advertising in Michigan to conserve funds.

For the past few presidential campaigns, the major-party candidates have avoided national advertising and instead concentrated their commercials in battleground states, said Evan Tracey, who heads the Campaign Media Analysis Group of Arlington. The strategy reflected the idea that national ads were both expensive and inefficient because there were relatively few "swing" voters left to convince in most parts of the country.

But both Obama and McCain have run national ads during this campaign, most notably during NBC's telecast of the Summer Olympics. They have also bought airtime on the networks' nightly newscasts.

Obama may be looking to boost not only his own candidacy through his CBS buy, but those of Democratic senatorial candidates, said West. Democrats, who now hold 51 seats (including two independents), are seeking a filibuster-proof majority of 60 seats in the Senate.

"When you have cash, anything is possible," said West. Obama "is not in a situation where he has to make resource trade-offs."" (Paul Farhi, The Washington Post, October 10, 2008)