It's common for historians to criticize Hubert Humphrey's failed 1968 campaign: he refused to take a strong stand on the war, declined to campaign with either Robert Kennedy or Eugene McCarthy after the bitter Democratic Convention, and failed to reveal that Nixon had interfered in the Vietnam peace talks.
But Humphrey's defenders rightly point out that Humphrey managed to narrowly edge out Nixon in the popular vote. Winning the election despite losing the popular vote fueled Nixon's paranoia and had a major impact on his actions while in office. Many writers attribute this to Sirhan Sirhan's attempted assassination of LBJ on June 5, 1968. After the attempt Johnson enjoyed a popularity boost that helped Humphrey on election day. While LBJ was always Sirhan's original target, he had also considered shooting RFK. Had he done so, Humphrey wouldn't have benefited from LBJ's improved popularity and Nixon might've won the popular vote.
The POD is that Sirhan tries to kill RFK instead. The attempt fails like in OTL, but Nixon defeats Humphrey in both the electoral and popular vote. Does this change anything? If so, how?