There's a big difference between:
1.) Stating that you are completely, positively against something, winning votes from it, and coming to a compromise that doesn't jeopardize these values (honest way)
2.) Stating that you are completely, positively against something, winning votes from it, and then once the political capital you gained from doing so runs out, coming to a compromise that completely throws these values under the bus (dishonest, old way)
Obama was campaigning as #1, his actions are #2.
EDIT: What GG said.