do you really want national coverage knowing how they would do it?
2+ hours of a marathon is plenty of time to do a human interest story on each of the runners in the race...and then do interviews with all the 2:22:0x guys who just missed it. They could sandwich all that in between the start and the finish with breaks for commercials, just like they do for the 10K at the track and field trials.
Coverage like that is what makes both the informed viewer, and the average joe 6 pack change the channel to catch poker.