As the 1960s progressed, McCarthy emerged as a prominent opponent of Johnson's handling of the Vietnam War. After Robert F. Kennedy declined the request of a group of antiwar Democrats to challenge Johnson in the 1968 Democratic primaries, McCarthy entered the race on an antiwar platform. Though he was initially given little chance of winning, the Tet Offensive galvanized opposition to the war and McCarthy finished in a strong second place in the New Hampshire primary. After that, Kennedy entered the race and Johnson announced that he would not seek reelection. McCarthy and Kennedy each won several primaries before Kennedy was assassinated in June 1968. The 1968 Democratic National Convention nominated Vice President Hubert Humphrey, Johnson's preferred candidate.