Defying these predictions, Truman won the election with 303 electoral votes to Dewey's 189. Truman also won 49.6% of the popular vote compared to Dewey's 45.1%, while the third party candidacies of Thurmond and Wallace each won less than 3% of the popular vote, with Thurmond carrying four southern states. Truman's surprise victory was the fifth consecutive presidential win for the Democratic Party, the longest winning streak for either party since the 1880 election. With simultaneous success in the 1948 congressional elections, the Democrats regained control of both houses of Congress, which they had lost in 1946. Thus, Truman's election confirmed the Democratic Party's status as the nation's majority party. This was the last presidential election before the admission of the Twenty-second Amendment in 1951, limiting the number of terms a person may be president.[7] This is the last time a Democrat won without New York, Pennsylvania, and Delaware, and the only time they have done so without Maryland. This was the first election that a Democrat won without the Deep South states of Louisiana, Mississippi, and Alabama, and the first since 1836 that they won without South Carolina, and the first since 1916 that they won without Oregon, New York, and New Jersey.
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What gets lost in all of this is that Dewey had huge rallies
He just didnt have the cahones to finish the job.