In 1948, Harry S. Truman and Alben W. Barkley were elected president and vice president of the United States, defeating Republican nominees Thomas E. Dewey and Earl Warren. Truman, a Democrat and vice president under Franklin D. Roosevelt, had ascended to the presidency upon Roosevelt's death in 1945. He announced his candidacy for election on March8, 1948. Unchallenged by any major nominee in the Democratic primaries, he won almost all of them easily; however, many Democrats like James Roosevelt opposed his candidacy and urged former Chief of Staff of the United States Army Dwight D. Eisenhower to run instead.

Truman wanted U.S. Supreme Court Associate Justice William O. Douglas to be his running mate. Douglas declined, claiming a lack of political experience; in reality, his friend Thomas Gardiner Corcoran had advised him not to be a "number two man to a number two man". Senator Barkley's keynote address at the 1948 Democratic National Convention energized the delegates and impressed Truman, who then selected Barkley as his running mate. When the convention adopted Truman's civil rights plank in a close vote of to , many Southern delegates walked out of the convention. After order was restored, a roll call vote gave Truman a majority of delegates to be the nominee; Barkley was nominated the vice-presidential candidate by acclamation.

The Progressive Party nominated Henry A. Wallace, a former Democratic vice president, to run against Truman. Strom Thurmond, the governor of South Carolina, who had led a walkout of a large group of delegates from Mississippi and Alabama at the 1948 convention, also ran against Truman as a Dixiecrat, campaigning for states' rights. With a split of the Democratic Party, most polls and political writers predicted victory for Dewey and gave Truman little chance.

During the campaign, Truman mostly focused on blaming the Republican-controlled Congress for not passing his legislation, calling it a "do-nothing Congress." In early September 1948, Truman conducted various whistle-stop tours across the nation, covering over on the Ferdinand Magellan railcar. Of all of the speeches which he gave during his whistle-stop tour, only about 70 were broadcast on the radio even locally, and only 20 of them were heard nationally. During the final days of the campaign, the Truman campaign released a film titled The Truman Story showing newsreel footage of the whistle-stop tour. Although he received some endorsements, including that of Screen Actors Guild president and future 40th president Ronald Reagan, most broadcasting companies were sure of Dewey's victory. Ultimately, Truman won with 303 electoral votes to Dewey's 189 and Thurmond's 39. Before the results were released, an early edition of the Chicago Daily Tribune wrongly anticipated the result with the headline "Dewey Defeats Truman". Time magazine later described an image of Truman holding the newspaper as the "greatest photograph ever made of a politician celebrating victory." Truman and Barkley were inaugurated on January 20, 1949. Truman's 1948 campaign and the election are most remembered for the failure of polls and Truman's upset victory.

Background

Harry S. Truman was born in Lamar, Missouri, in 1884. After graduating from Independence High School in 1901, he enrolled at the Spalding's Commercial College, but dropped out within a year. When the United States entered World War I in 1917, Truman joined BatteryB, successfully recruiting new soldiers for the expanding unit, for which he was selected as their first lieutenant. By July 1918, he became commander of the newly arrived BatteryD of the 129th Field Artillery, 35th Division. After the war, he was elected the Presiding Judge of Jackson County, Missouri, and later served as a senator from Missouri. As a senator, he was head of the Senate Special Committee to Investigate the National Defense Program, known as the Truman Committee.

By 1944, most of the advisors of the incumbent President Franklin D. Roosevelt believed that he might not live out a fourth term and that his vice president would likely become the next president. Most of Roosevelt's advisors viewed the incumbent Vice President Henry A. Wallace as too liberal. In 1944, Roosevelt replaced Wallace from his ticket with Truman. Despite showing little interest in being vice president, Truman was selected by the 1944 Democratic National Convention as the nominee. The Roosevelt–Truman ticket won the presidential election, defeating the Republican ticket of Thomas E. Dewey and John W. Bricker. Truman was sworn in as vice president on January20, 1945. He had been vice president for 82 days when Roosevelt died on April12, making Truman the 33rd president. Truman later said: "I felt like the moon, the stars, and all the planets had fallen on me."

Truman asked Roosevelt's cabinet members to remain in their positions, telling them he was open to their advice. He emphasized a central principle of his administration: he would be the one making the decisions, and they were to support him. During World War II, with the invasion of Japan imminent, he approved the schedule for dropping two atomic bombs to avoid a costly invasion of the Japanese mainland. It had been estimated the invasion could take a year and cause 250,000 to 500,000 American casualties. The United States bombed Hiroshima on August6, and Nagasaki three days later, leaving approximately 105,000 dead; Japan agreed to surrender the following day. Truman said that attacking Japan in this way, instead of invading it, saved many lives on both sides. With the end of World WarII, Truman implemented the Marshall Plan, allocating foreign aid for Western Europe. Apart from primaries and campaigning in 1948, Truman dealt with the Berlin Blockade, which is considered the first major diplomatic crisis of the Cold War. During Truman's presidency, his approval ratings had dropped from 80 percent in early 1945 to 30 percent in early 1947. The 1946 mid-term election alarmed Truman when Republicans won control of both houses of Congress for the first time since the 1920s. In 1947, Truman told his Secretary of Defense James Forrestal that, except for the "reward of service", he had found little satisfaction in being president.

Gaining the nomination Preparing for a run In December 1947, former Vice President Wallace had announced via radio that he would seek the presidency in 1948 as a third-party candidate. He was dissatisfied with Truman's foreign policy, and in his announcement, made an attempt to link Truman to a war-oriented point of view. The previous year, Truman had demanded and received his resignation from the cabinet as the Secretary of Commerce. Due to his declining popularity, Truman had initially decided not to run. He considered former Chief of Staff of the Army General Dwight D. Eisenhower as an ideal candidate for the Democrats, and persuaded him to contest the presidency. In a public statement, however, Eisenhower declined all requests to enter politics, without disclosing his political party affiliation. Momentum among Americans for Democratic Action (ADA) members and politicians grew for the Draft Eisenhower movementto the extent that some Democratic politicians began organizing a "Dump Truman" effort to persuade Eisenhower to run as a Democrat. According to Secretary of the Army Kenneth Royall, Truman even agreed to run as the vice-presidential nominee of Eisenhower, if he so desired, but all efforts to persuade him failed.

In early 1948, Truman agreed to contest the presidency, asserting that he wanted to continue contributing to the welfare of the country. His advisor, Clark Clifford, later said that the greatest ambition Truman had was to be elected in his own right. His candidacy faced opposition within the Democratic Party from the progressive movement led by Wallace, and the states' rights movement led by South Carolina Governor Strom Thurmond. In November 1947, Democratic political strategist James H. Rowe wrote a memo titled "The Politics of 1948", highlighting the challenges and the road map for Truman's campaign. Clifford edited and presented the forty-three page confidential memo to Truman, which stated: "The Democratic Party is an unhappy alliance of Southern conservatives, Western progressives, and Big City labor." Rowe accurately predicted Dewey would win the Republican nomination, calling him a "resourceful, intelligent and highly dangerous candidate". Rowe also warned of the potential threat from Southern Democrats and Wallace. The Rowe–Clifford memo advised Truman to project himself as a strong liberal and focus his campaign primarily on urban blacks, labor, and farmerswho made up the core of the New Deal coalition. Although Truman did not trust Rowe because of their difference of opinion in the past, he endorsed the strategy.

In his 1948 State of the Union address, Truman emphasized civil rights, saying: "Our first goal is to secure fully the essential human rights of our citizens." On March8, 1948, Democratic National Committee Chair J. Howard McGrath officially declared Truman's candidacy. He said: "The president has authorized me to say, that if nominated by the Democratic National Convention, he will accept and run." The presidential primary contests began the next day with the New Hampshire primary. Truman won the support of all unpledged delegates unopposed. He faced little opposition in the primary contests, as he was the sole major contender. He won almost all the contests by comfortable margins, receiving approximately 64 percent of the overall vote. Despite his performance in the primaries, Gallup Poll indicated no matter how Truman might campaign, he would lose in November to any of four possible Republican nominees: Dewey, Arthur Vandenberg, Harold Stassen, or Douglas MacArthur.

Historian and author Andrew Busch described the political scenario as: Americans in 1948 had to render judgment on three major policy innovations. It was the first presidential election since depression, war, and the presence of FDR in which the nation could take stock of the New Deal direction of domestic policy. It was also the first election after the establishment of containment as the foreign policy of the United States and the first since Truman had made civil rights an important part of the federal policy agenda... The presidential nominating system in 1948 was substantially different from the reformed system to which we are accustomed, and the differences were important. Primary elections influenced the nomination but did not control it; it was possible to seriously consider a genuine last-minute draft of a candidate; and the national conventions really mattered.

Early developments