Humphrey entered the race after Johnson 's withdrawal , making the 1968 Democratic primaries a three-way contest between Humphrey , Kennedy , and McCarthy . Kennedy cut into McCarthy 's liberal and anti-war base , while also winning the support of the poor and working class . He won a series of primary victories , but was assassinated in June by Sirhan Sirhan , an Arab nationalist . With Johnson 's support , Humphrey won the presidential nomination at the tumultuous 1968 Democratic National Convention , held in Chicago in late August . The violent clashes in Chicago between anti-war protesters marred the convention . After the convention , polls showed Humphrey losing the general election by 20 points
1968 Democratic National Convention
1968 Democratic National Convention
Presidency of Lyndon B. Johnson