As the United States entered World War I and women became more deeply involved in the war effort, it became impossible to justify denying them the vote as a constitutional matter. In 1918, the push for an amendment got the backing of President Woodrow Wilson. It passed Congress in June 1919, and the states quickly began to ratify it. The primary opposition to women’s suffrage was the same as it was for black suffrage: southern white Democrats, most of whose states would refuse to ratify the Nineteenth Amendment until the 1950s. Mississippi held out until 1984.