The Democratic Party , which controlled the House of Representatives , the Senate , and the White House , was divided in 1968 . Senator Eugene McCarthy entered the campaign in November 1967 , challenging incumbent President Johnson for the Democratic nomination . Robert F. Kennedy entered the race in March 1968 . Johnson , facing dissent within his party , and having only barely won the New Hampshire primary , dropped out of the race on March 31 . Vice President Hubert Humphrey then entered into the race , but did not compete in any primaries ; he inherited the delegates previously pledged to Johnson and then collected delegates in caucus states , especially in caucuses controlled by local Democratic party leaders . After Kennedy 's assassination on June 5 , the Democratic Party 's divisions grew . At the moment of Kennedy 's death the delegate count stood at Humphrey 561.5 , Kennedy 393.5 , McCarthy 258 . Kennedy 's murder left his delegates uncommitted
Kennedy 's assassination on June 5
Assassination of Robert F. Kennedy
1968 Democratic National Convention