Today on "World News with Charles Gibson":

Presidential Politics:
Was Barack Obama comparing Gov. Sarah Palin to a pig Tuesday when he said, "If you put lipstick on a pig, it's still a pig"? John McCain's campaign claims he was, but Obama says he was referring to the McCain-Palin economic policy and accused the McCain campaign of playing up phony outrage. What's going on with our political discourse? ABC's political team has the latest on the candidates' tactics on the campaign trail.

Dog Days of Summer:
Alaska's Iditarod race is a grueling test of survival for dogs that pull snow sleds over a thousand miles in subzero temperatures. But how do trainers keep the dogs in shape during Alaskan summers? Four-time Iditarod champion Jeff King has developed a new technique to keep these canine athletes fit when they can't race through the snow -- swimming. ABC's Neal Karlinsky explains.

And on our "World News webcast", along with our top headlines:

Facebook Face-Lift:
The 100 million users of the social networking site Facebook are being forced to adapt to a redesigned Web site, whether they like the new look or not. But not all Facebook members are happy -- groups and petitions have already cropped up to protest the change. What's going on with Facebook? The webcast has the latest.