Obama buys half hour of primetime TV

Barack Obama has purchased a half hour of primetime television for a campaign advert.

The Democrat presidential candidate's broadcast will appear on CBS and NBC in the week running up to the American election. It will air at 8pm on Wednesday, October 29.

Republican Ross Perot adopted a similar campaign strategy in 1992.

Political analyst Larry Sabto told The Hollywood Reporter: "Obama's theme is not just change but unity, so he's appealing to the whole nation rather than a handful of tossup states.

"He wants to win the popular vote by a good margin, which will enable him to govern."

Obama's rival John McCain is unlikely to copy the move due to financial restraints on his campaign. McCain accepted public financing, which means he is limited in the amount of money he can raise and spend.

"There will be no second-guessing the Obama campaign on decisions involving resources," said campaign media analyst Evan Tracey.

"He's not doing this and pulling down [ad] buys in Florida. This is not an either/or decision. They've got 25 days and unlimited amounts of money."

The advert is likely to mean that CBS comedy The New Adventures Of Old Christine will be pushed to 8.30pm, while NBC is expected to replace an hour-long Knight Rider with a half-hour comedy repeat.