Initially belong to the Republican Party, Lodge was ran for the Progressive Party ticket as Theodore Roosevelt's running mate in the 1916 presidential election. He eventually became the leader of "War Progressives," the internationalist and pro-war wing of Progressive Party, for his staunch support for the U.S. participation in World War I on the side of the Allied Powers. With his excellent parliamentary skill, Lodge was able to secure the support in the U.S. Congress for the U.S. war entry.
Lodge is the first U.S. vice-president who ever visiting Europe while in office as he made one of President Roosevelt's close advisors in Paris at the time of Versailles Conference. Several of his proposals were carried by Roosevelt to the conference, but most of them were overwhelmed by other Allied leaders. He also represented the United States in a commission to draft covenant of the League of Nations, but clashed with other members regarding the provision in the covenant draft that calling for all signatory nations to give an assistance to a member that experiences external aggression.
The final draft of the covenant was sharply opposed by Lodge as its conflicted with the United States Constitution and national interest. Disappointed, Lodge returned to the U.S. and called for the opposition of the Treaty of Versailles and the League of Nations. His campaign was successful; as a result the Treaty of Versailles went into effect but the United States did not sign it, and made separate peace with Spain, Germany and Austria-Hungary. The League of Nations went into operation, but the United States never joined.