If that happened, I'd think that LBJ gets two terms if the economy is OK as per OTL and the GOP still nominates Goldwater. Nixon will not run in '64, and I don't know how LBJ would handle the Missile Crisis if it occurred. Perhaps a withdrawal from Vietnam, or an escalation, since both were still feasible then. RFK will not work for Lyndon Johnson, most certainly not for two terms. He'll be a political nobody unless he runs for Congress, not Senate, in 1962. Maybe he could still win the special election for his brother's seat thanks to the field army in MA. Do not expect a POTUS run, depending on his legislative output, until 1976 at the earliest. Nixon in '68 if things go according to OTL. I've laid out a prospective RFK Presidency in Resurrection City.