Hillary Clinton and Barak Obama are afraid to debate in New Hampshire. All the Republican candidates and all the Democrat candidates except for Barak and Hillary have agreed to debates in New Hampshire.
Clinton is the clear front runner in the primaries and does not want to give anybody the chance to challege her and is probably why Hillary is avoiding debating Hillary in New Hampshire.
Obama has caught up to Clinton in the polls in New Hampshire and elsewhere. Who knows exactly why people like Obama but he has caught up in popularity and does not want to remind voters by debaing that they can choose a slick white man like Edwards or someone with kick ass foreign policy experience like Bill Richardson.