I'm not sure about this because of the act that Vito took Tom aside to tell him "I never thought you were a bad consigliere, I thought Santino was a bad Don, rest in peace." But then again Vito did acceed to Michael's wish that Tom not be a part of the 1955 Massacre becaue he was not a wartime consigliere.

Going back to TB's hypothesis for a political career for Michael, I agree he could have made it to congress and then gerrymandered a district that could have kept him there for life. This may have been enough for him to conrol powerful committees and build a machine in New York City and State that could, through surrogates help the Corleones in numerous ways.
I don't think Michael could win NY .. because of the prejudice. He wouldnt get a vote north of Westchester County.