I can’t see Bobby Kennedy fulfill any of his promises or policy goals while winning re-election in 1972. Peace in Vietnam would have to be hard fought. War hawks won’t like that an explicitly anti-war candidate got elected during a war and everybody from the South Vietnamese regime to the conservatives in Congress would have an issue with RFK calling for a swift end to the war. Either he gets bogged down trying to bend over backwards to make a treaty that would please hawks and S. Vietnam (which would be tough under any circumstance) and risk a surge in unpopularity with the public thinking the US is abandoning the war. Or he could get bogged down in the fighting, looking for one big win to claim a victory and lock down right wing support for a negotiated peace, which would take a long time and cost him the support of the anti-war left that is his base. It would take a genuine miracle for him to please everybody, end the war, and be popular enough to win re-election. That would be a miracle too far for Robert Kennedy after having survived a bullet, won the nomination, and then the presidency.
I think he’d lose re-election to just about any Republican they could run outside of a hardcore ideologue like Reagan (who he might be able to narrowly beat) or extremely corrupt and bad at hiding it types like Spiro Agnew. I think somebody like Charles Percy or Howard Baker or John Volpe would be the one to win it that year, projecting a clean, moderate image untainted by having just had to negotiate the end to a war that many are definitely unhappy with.