On March 12, McCarthy won 42 percent of the primary vote to Johnson's 49 percent, an amazingly strong showing for such a challenger. Four days later, Senator Robert F. Kennedy of New York entered the race. Internal polling by Johnson's campaign in Wisconsin, the next state to hold a primary election, showed the President trailing badly. Johnson did not leave the White House to campaign.
By this time Johnson had lost control of the Democratic Party, which was splitting into four generally antagonistic factions. The first consisted of Johnson (and Humphrey), labor unions, and local party bosses led by Chicago Mayor Richard J. Daley. The second group consisted of students and intellectuals who were vociferously against the war and rallied behind McCarthy. The third group was Catholics, Hispanics, and African Americans, who rallied behind Robert Kennedy. The fourth group was traditionally segregationist white Southerners, who rallied behind George C. Wallace and the American Independent Party. Vietnam was one of many issues that splintered the party, and Johnson could see no way to win the war[193] and no way to unite the party long enough for him to win re-election.