Senator Kennedy had finished second on the vice presidential ballot of the 1956 Democratic National Convention. After Republican President Dwight D. Eisenhower was reelected over Adlai Stevenson in the 1956 presidential election, Kennedy began to prepare a bid for the presidency in the 1960 election. In January 1960, Kennedy formally announced his candidacy in that year's presidential election. Senator Hubert Humphrey of Minnesota emerged as Kennedy's primary challenger in the 1960 Democratic primaries, but Kennedy's victory in the heavily-Protestant state of West Virginia prompted Humphrey's withdrawal from the race. At the 1960 Democratic National Convention, Kennedy fended off challenges from Stevenson and Senator Lyndon B. Johnson of Texas to win the presidential nomination on the first ballot of the convention. Kennedy chose Johnson to be his vice-presidential running mate, despite opposition from many liberal delegates and Kennedy's own staff, including his brother Robert F. Kennedy. Kennedy believed that Johnson's presence on the ticket would appeal to Southern voters, and he thought that Johnson could serve as a valuable liaison to the Senate.