It was not the power of the opposition forces, liberal or conservative, of the U. that led to the final defeat of the Treaty of Versailles, but rather the political ignorance, inability and inflexibility of the President, Woodrow Wilson. With the surrender of Germany after WW1, it presented many different ways to create peace. Wilson in 1918 offered his plans for peace in the "Fourteen Points", the most important of which he believed was Article X, the League of Nations. One year later, Wilson led the Paris Peace Conference at Versailles to reach an international pact that included the points. However, the U.S. was never to sign the treaty or join the League of Nations.
Woodrow Wilson's ideas for peace were well rooted in thought, but in politically applying his ideas, he made unchangeable mistakes. In heading up the peace conference, Wilson made a serious mistake by not including the representation of the legislative body, not selecting the Republicans to take on the assignment, and not discussing with the "Republican authority" in the Senate, Henry Cabot Lodge, head of the Foreign Relations Committee. As shown in the Tribune's political cartoon, the U.S. was becoming wrapped up in foreign matters without the support of the Senate. The Constitution of the U.S. calls for the Senate ratification of all treaties to end wars, and Wilson overlooking the Senate's representation may not have followed the constitution.
In trying to win support for the League of Nations, which he personally believed was the moral cause of the "war to end all wars", Wilson was once again weak and created an even deeper division in his relationship with the Senate. Henry Cabot Lodge was willing to accept the treaty with one condition: that the U.S. would not go to war to defend a country in the League of Nations without having the approval of Congress. Wilson was unwilling to compromise on this issue, and made the situation even worse when he called on the Democratic Party to oppose Lodge's doubts and elect a Democratic president in the upcoming election to be able to ratify the treaty.