Exclusive: Obama buys half-hour of network primetime--The Live Feed

The Live Feed has the Exclusive:

Barack Obama has purchased a half-hour of airtime on CBS, sources confirm.

The Obama campaign will air a half-hour primetime special on Wednesday, Oct. 29, at 8 p.m.

Sources say the Obama camp is also in talks with NBC and Fox. NBC is said to be very near a deal. With Fox, the matter is likely to remain uncertain as the time period could conflict with Game 6 of the World Series.

A CBS spokesperson declined comment. The buy will push comedy "The New Adventures of Old Christine" to 8:30 p.m. and pre-empt "Gary Unmarried." The buy is being placed by Washington-based ad firm GMMB.

The direct purchase of such a large block of national airtime right before an election used to be more commonplace before campaigns began to focus their end game strategies exclusively on battleground states. Such a move is not without precedent in modern presidential politics, however -- Ross Perot did a similar purchase in 1992.