dr. martin luther king jr. was assassinated, robbette kennedy assassinated, richard nixon elected president and so much more. joining us to discuss this is historian and author douglas brinkleyl conversations recorded by president nixon in the years following the '68 election. great to have you with us, doug. >> thanks for having me. >> when we think of the '60s it means a lot of things to different people. one of the things the '60s means is turmoil. when we think of turmoil, that's 1968. was there one thing that set it off or was it a combination of factors? >> i think it was the tet offensive in early '68 in vietnam, where the vietcong and the north vietnamese were able to sack some of south vietnam, do damage to our embassy in saigon. it started telling the american people just starting the year '68 we weren't winning in vietn vietnam. it's a chain effect. the tet offensive happens and lyndon johnson in march goes on television says i'm not going to seek re-election because i'm so mired. then it becomes a free-for-all with utheen mccarthy and bobby kennedy starting to fight for being the dove candidate of vietnam and the tragedies, the deaths, as you mentioned, of bobby