LOS ANGELES — A half-hour Barack Obama campaign ad will blanket the major broadcast networks at 7 tonight — except for ABC.

Attempting to protect its struggling Wednesday lineup, ABC tried to reach an agreement with the Obama campaign to air the commercial on a different night, according to people familiar with the discussions who requested anonymity because they were not authorized to comment publicly.

ABC had a change of heart, but by the time it decided to make the Wednesday slot available for the Democratic presidential candidate's spot, his campaign had already finalized the ad buy, the people said. ABC will air an episode of the hourlong "Pushing Daisies" at that time, as scheduled.

The Obama campaign bought time on CBS, NBC and Fox for $1 million per network.

The 30-minute spot, which was announced in early October, will air six days before the election between Obama and Republican candidate John McCain. It is also scheduled to run on Univision, BET, MSNBC and TV One.

Described by the Obama campaign as a "program," the half-hour will present "the specifics of Obama's plans to turn the economy around and get the country back on track," according to campaign spokesman Nick Shapiro.