Woodrow Wilson - After the 1912 election, nothing really went his way. Isolationism was a great policy and all, but he allowed Germany to sink so many of our ships and failed to negotiate peace talks. Then after declaring war which he really didn't want to do to begin with, he got even more hate from citizens of German, Austrian-Hungarian, Bulgarian or Turkish descent and also in part due to the 18th Amendment, his party lost control of Congress to the Republicans which really changed the outcome of what could have been Wilson's greatest U.S. accomplishment. Congress went against his proposal at the Treaty of Versailles for a League of Nations and President Wilson ended up getting paralyzed from campaigning across the country to hard for it which ended his political career and never got to run again in 1920.
Wilson was no isolationist. He was an Anglophile who was dealing with a traditionally isolationist public but who was consistently as pro-Entente as he could get away with. His sham neutrality is what allowed him to eventually draw the United States into the war when it became clear that without American troops and money, the Entente would lose the war.
If anything, Wilson should be considered one of the luckier U.S. politicians. Without the Republican infighting in 1912, he never would have gotten to be president. Without the European fighting in 1916, it is doubtful he could have ever gotten reelected.
