His support for wartime legislation was not absolute as Smith objected to sections of the Sedition Act of 1918 which required proof of intent during the commission of sedition. In addition to war-related activities, Smith served as a floor leader for ratification of the Migratory Bird Treaty Act of 1918. During the third session of the 65th Congress, Smith joined with Senator Ashurst in a call for the United States to purchase Baja California from Mexico. The 1918 Senate elections returned control of the Senate to the Republicans. Smith voted for the 19th Amendment to the U.S. Constitution, granting Women's suffrage but was absent from much of the 66th United States Congress' first session. He was instead occupied in Kentucky visiting sick relatives. When President Woodrow Wilson proposed creating the League of Nations, Smith became an avid supporter of the plan. Despite his advancing age, Smith was determined to win another term in the election of 1920. The senator's support for the League of Nations became a campaign issue. Meanwhile, labor unions were upset with the senator over his voting record on labor issues. He overcame these issues to win the Democratic primary. During the general election, Ralph Cameron attacked Smith on these two issues and added that while Smith had found time to visit Kentucky he had rarely returned to Arizona during the previous six years. Smith countered by pointing out that there had been no Senate recess long enough to allow for a trip from Washington D.C. to Arizona. Smith could not overcome these issues and lost in the general election. The loss of his reelection bid left Smith embittered. Additionally, his remaining financial resources were limited and Smith found himself in need of a job. To address these concerns Smith's friend, Epes Randolph, told him "Mark, you should go back to Washington and say to President Wilson, 'Mr. President, I've made a damn fool of myself over you a good many times—now you make a damn fool of yourself over me just once—give me some kind of a job'" Smith followed this advice and was appointed to the International Joint Commission on March 3, 1921, the last full day in office for both the Senator and President. During his final years, Smith lived in Washington's Occidental Hotel, taking occasional trips to Kentucky to visit his remaining family. In Washington, he received only occasional visits from a niece living in Kentucky. The solitude bothered him as shown in a January 1924 note where he wrote: "was surenuff lonesome and hungry to hear something of old friends." His health also began to decline as he developed arthritis in his left hip.