Updating the Presidential Campaigns after Nevada, South Carolina

After South Carolina, the New York Times says John McCain is the Republican front-runner, whether he likes it or not. On the Democratic side, after Nevada, Barack Obama is running against two Clintons, rather than just one. Is former "maverick" John McCain now the Republican front-runner? Can Rudy Giuliani finally get underway in Florida? After Nevada, is Bill doing Hillary more harm than good? Is Obama right to challenge both Clintons at the same time? Will John Edwards turn out to be the king—or queen—maker at the Democratic National Convention? Last weekend's results produced new challenges for the candidates of both political parties. We hear what's next on the campaign trails.