Wilson presented the Versailles treaty to the Senate on 10 July 1919, in the supreme confidence that that body would not dare to refuse to give its consent to ratification. There were many signs of danger ahead. One was the persistence of the tradition of isolationism, which before 1914 had been the cornerstone of American foreign policy. Ratification of the Treaty of Versailles would carry heavy new international responsibilities for the United States: Article 10 of the covenant guaranteed the political independence and territorial integrity of all member nations, and support of the covenant's peacekeeping machinery might well entail the risk of war. Moreover, Republicans controlled the Senate, and Wilson's implacable personal and political foe, Henry Cabot Lodge of Massachusetts, was chairman of the Foreign Relations Committee.
Lodge would have preferred to reject the treaty outright, but in order to preserve unity within his party, he accepted a plan offered by more moderate Republicans—to approve the treaty subject to certain reservations. The most important of these was a reservation to Article 10 that stipulated that the United States assumed no obligation under this article unless Congress, by joint resolution or otherwise, should specifically assume such obligation.
Saying that the enemies of the League were poisoning the wells of public opinion, Wilson set out upon a tour of the West in order to purify them. In one of the great forensic efforts in American history, he traveled eight thousand miles and delivered thirty-two major addresses between 3 and 25 September 1919. During the early hours of 26 September, Wilson suffered a stroke warning, which ended his tour. Then, on 2 October, after his return to Washington, Wilson suffered a devastating stroke that paralyzed his left side and for a time threatened his life.
This stroke was only the worst manifestation of cerebrovascular disease that had victimized Wilson at least since 1896, when he suffered loss of dexterity in his right hand for about eight months. Then came small strokes and a serious vascular accident in his left eye in 1906. Dr. S. Weir Mitchell, the distinguished neurologist of Philadelphia, examined Wilson soon after the election of 1912 and reported to the White House physician, Dr. Cary T. Grayson, that he thought Wilson would not live out his first term. Grayson kept Wilson on a regime of simple diet, exercise, and avoidance of stress, but the tasks of overseeing the American war effort blew Grayson's regimen to pieces. Wilson, now suffering from uncontrolled hypertension, went to Paris unwell. There he suffered a viral infection and another small stroke in April 1919. This was followed by a more severe small stroke on 19 July. By the time Wilson went out West, his hypertension was fulminant. The specialist who examined Wilson after his large stroke of October reported that he had long suffered from hyper-tension, atherosclerosis, and carotid artery disease and was in the lacunar state as a result of small strokes. Wilson was almost completely disabled, both physically and psychologically, from October through December 1919.
A healthy Wilson would almost certainly have found a high ground of compromise with pro-League Republicans and put the treaty across, probably by October 1919. But the sick Wilson, isolated in the White House, was incapable of comprehending political realities, or even of thinking abstractly or strategically. When the treaty came up for a vote in the Senate on 19 November, Wilson commanded Democrats in the Senate to vote against ratification with reservations. The reservation to Article 10, Wilson said, amounted to nullification, not ratification, of the treaty. The Republicans defeated ratification without the reservations; the Democrats then defeated ratification with the reservations.
Democrats tried to find some compromise, but Lodge would not budge on the all-important reservation to Article 10. For his part, Wilson not only refused to yield an inch of ground, but in a public letter (drafted, actually, by his chief of staff, Joseph P. Tumulty), on 8 January 1920 he also made the League issue a partisan question by saying that the coming presidential election should be a "great and solemn referendum" on the question of ratification of the Versailles treaty. Actually, all hopes for Senate approval were by now dead unless enough Democrats were prepared to defy Wilson and join the Republicans to form a two-thirds majority in favor of ratification with reservations. And if that had happened, Wilson would have killed the treaty himself by refusing to go through the process of ratification. But Wilson did not have to do this. In one of the most important presidential letters in history (drafted for the most part by Tumulty), written to his spokesman in the Senate on 8 March 1920, Wilson commanded Democratic senators to vote against ratification with any reservations whatsoever. A second vote in the Senate, on 19 March 1920, failed to find two-thirds of the senators in favor of the treaty in any form. Wilson was only momentarily downcast, if at all. He planned to secure his renomination and to run again for the presidency on a pro-League platform.