A telling line left out of the movie but in the saga is in the scene when Michael first comes home and tells Vito that his giving in on the drug issue could be construed as a sign of weakness. Vito corrects him and he says is IS a sign of weakness, so however the family was being run, they had a sick Vito who lacked the necessary stamina, and Tom and the Capo Regimes trying to hold it together. SO however things were run after Sonny's death the family was certainly not gaining strength.
Vito definitely looked weakened in that scene, and the family was not gaining strength. But Vito had to appear weak in order to gain the truce and agreement that would enable him to bring Michael home. And, as we saw, Michael continued the "weak" look--until the Great Massacre of 1955 put the Corleones back on top again.
As for the point about what would have hapened to Michael if Sonny lived, that's a tough one. I think Michael with his
"I'm with you Pop" and his murder of Sollozzo and McCluskey "crossed the Rubicon" and could never go back to become a lawyer or a Senator. Not shown in the movie is how someone else took the rpa for what Michael did, but I don't think anyone really believed it as witnessed by the questioning of Michael years later in the Senate hearing. He was way too mobbed up to hold public office. Besides, Hagen was already there as a lawyer, so what role Michael would play with SOnny alive is tricky. My best guess is that he would come into the family business and use his guile, cunning and intelligence to maneuver Sonny to do his bidding without Sonny realizing it.
Additionally Sonny being the loose cannon that he was there was a good chance he'd have done something else to get himself killed anyway.
Also, had he lived and Michael returned even Vito could have put Michael in charge of the family business and move Sonny into the background as consigliere or co-consigliere. He could say his affair with Lucy Mancini and the birth of Vincent Mancini was an infamnia for which he had to be punished.
Logic is on your side, dt. But, in the vein of "difficult, not impossible":
As we know from the novel, the Bocchicchios created a plausible alibi for Michael re. the Sol and Mac murders. Once back in America, Michael could have finished college and law school. He'd then run for Congress in Vito's old stamping grounds in Little Italy, where the Corleone name and political influence would be an asset. A smart guy like Michael would compile a solid record and many political alliances in the House, while making sure he kept his family ties way in the background: Kay,
si, Vito and Sonny,
no.
Running for the Senate or the Governorship would be more difficult. Prejudice against Italians, combined with his family background, would work against him big-time. But it's possible that Michael could project a popular image, label the accusations as "bigotry," and buy off or intimidate his opponents.
If he won a Senate seat or the Governorship,
then I believe he'd act on Vito's long-standing desire to "legitimize" the Corleone business. Michael would work to legalize gambling, either nationwide or in New York, thus channeling the Corleones' dominance of illegal gaming into legitimate casinos and sports-betting outlets. He'd also channel Vito's union strongholds into his own political machine, and use his influence with labor to broker support from other politicians: "Vote for my gaming bill and I'll make sure the unions contribute to your re-election campaign and turn out members to vote for you."
A longshot,
but just barely possible...
