In early 1970, Representative Tunney announced that he would seek the Democratic nomination for the Senate. His announcement was followed by that of fellow congressman George Brown, Jr. Their primary battle turned into one of the most bitter in California history. One of the key issues was the military draft. While Brown and Tunney both questioned expanding U.S. involvement in Vietnam, Brown opposed a continuation of the military draft while Tunney favored it. This conflict gave incumbent Republican George Murphy an early lead in the polls. Murphy's staunch support for the Vietnam War hurt his campaign and as the general election approached, Tunney overtook him in the polls. The Murphy campaign suffered another setback when he underwent surgery for throat cancer, weakening his voice to a whisper. The Tunney campaign used his youthful appearance and high energy to contrast with the aging Murphy. His hairstyle and mannerisms drew comparisons to Robert F. Kennedy. Ultimately, Californians split their ticket in the 1970 midterm election, re-electing Republican governor Ronald Reagan and electing Democrat Tunney to the Senate.
