Maybe Barack Obama and Hillary Rodham Clinton can sum up their policy differences in 30 seconds or less on Wednesday night.

They will have to if they are going to get their points across well on networks other than ABC, which is sponsoring the hotly anticipated Democratic debate that evening. According to the usage guidelines circulated by ABC, other news organizations are only allowed to excerpt half a minute from the broadcast.

That means choosing only one 30-second clip to use on television and the Web between 11 p.m. Wednesday and 5 a.m. Thursday.

ABC defends the restrictions as being “very reasonable.” After all, ABC is footing the bill to stage the debate at the National Constitution Center in Philadelphia.

“We have an obligation to our West Coast affiliates to not make chunks of the debate available until their viewers have had a chance to see them,” an ABC spokesman said.

By tape-delaying the debate for its West Coast television stations, the network seems to be treating the debate as a television show rather than as a live news event. When cable news channels sponsor debates, they telecast the forums live across all time zones.

Indeed, the cable news channels may make it their business to skirt ABC’s rules. Fox News, CNN and MSNBC can be expected to use “fair use” justifications to show more clips from the debate, especially if the two candidates have a newsworthy exchange.

Bill Carter contributed reporting.