Not to be a pedantic asshole, but the question was about the political fallout of him not being court martialed. If he wasn't, he probably stays in the Navy to help boost the Patriotism Points of his older brother, Joe Jr., who was groomed for the Presidency. While IOTL Joe lost the Presidency (partially because of that very court martial and also because he cheated on his wife and was an asshole about it) this could turn his chances around and put him in the Oval Office. I don't actually know much about him, minus that he was a Senator, and he ran for President in '60 and lost spectacularly to Richard Nixon, so what he does there is up to people who know what they're talking about. Him not being convicted also sets a different precedent for court martialing someone for sinking-- if it's not explicitly the captain's fault, they may not be able to convict. That's actually a good thing; the Navy used to sabotage and then court martial black or female captains for sinking and that removes the loophole.