Humphrey's campaign concentrated on winning the delegates in non-primary states, where party leaders controlled the delegate votes. Kennedy defeated Branigin and McCarthy in the Indiana primary, and then defeated McCarthy in the Nebraska primary. However, McCarthy upset Kennedy in the Oregon primary.
After Kennedy's defeat in Oregon, the California primary was seen as crucial to both Kennedy and McCarthy. McCarthy stumped the state's many colleges and universities, where he was treated as a hero for being the first presidential candidate to oppose the war. Kennedy campaigned in the ghettos and barrios of the state's larger cities, where he was mobbed by enthusiastic supporters. Kennedy and McCarthy engaged in a television debate a few days before the election; it was generally considered a draw. On June 4, Kennedy defeated McCarthy in California, 46% to 42%, and also won the South Dakota primary held the same day. McCarthy refused to withdraw from the presidential race and made it clear that he would contest Kennedy in the upcoming New York primary, where McCarthy had much support from antiwar activists in New York City.