Theodore Roosevelt was shot on October 14, 1912, while giving a campaign speech in Milwaukee. His second term had ended in 1908, and he had been succeeded by William Howard Taft, his hand-picked successor. Prior to the 1912 election, Taft and Roosevelt broke over the future direction of Republican Party, which led Roosevelt to run for the Republican nomination. After defeat in the Republican primary, Roosevelt start his own party, the Progressive Party.

This assassination attempt is famous because Roosevelt allegedly continued speaking even after he was shot, only seeking medical attention after he finished his speech. Despite this obvious energy, Taft and Roosevelt would go on to split the Republican vote, resulting in the election of Woodrow Wilson.

-if you want to know more about Roosevelt and Taft, I'd recommend Doris Kearns Goodwin's book The Bully Pulpit.