After winning election to the United States Senate in 1905, La Follette had emerged as a leader of progressives. He sought the Republican presidential nomination in the 1912 election, but many of his backers switched to Theodore Roosevelt after the former president entered the race. La Follette refused to join Roosevelt's Progressive Party, and that party collapsed after 1916. However, the progressives remained a potent force within both major parties. In 1924, La Follette and his followers created their own Progressive Party which challenged the conservative major party nominees, Calvin Coolidge of the Republican Party and John W. Davis of the Democratic Party.