One-third of the Senate and all of the House of Representatives were elected in November, 1918. Many of the old members were re-elected, some friends and some enemies of the Federal Suffrage Amendment. The Republicans had a large majority and both parties wanted an early vote on it. President Wilson made this possible by calling a special session to meet May 19, 1919. Representative Frank W. Mondell (Wyo.) was elected majority leader of the House and Representative James R. Mann (Ills.) appointed chairman of the Committee on Woman Suffrage, both Republicans. The resolution for the Federal Amendment was introduced by six members on the opening day and on the 20th was favorably reported by the committee and placed on the calendar for the next day, even before the President's message was read, in which it was recommended. On May 21, after two hours' discussion, it was passed by 42 more than the needed two-thirds. The vote stood as follows:
| In Favor | Opposed | |
| Republicans | 200 | 19 |
| Democrats | 102 | 70 |
| Miscellaneous | 2 | 0 |
| 304 | 89 |
Members from southern States cast 71 of the affirmative votes and four from the North were born in the South. The Democrats polled 54 per cent. of their voting strength for the amendment and the Republicans polled 84 per cent. of theirs.
In all the great area west of the Mississippi River, excluding Texas and Louisiana, only one vote in the lower house was cast against the amendment—that of Representative H. E. Hull (Rep.), Iowa. In the group of Middle States only five opposing votes were cast—two from Wisconsin, one from Michigan, two from Ohio. The opposition centered in the coast States from Louisiana to Maryland; aside from these the largest opposing majorities were from Pennsylvania and Massachusetts. Twenty-six States—over half of the whole number—gave unanimous support; thirteen had large favorable majorities; one was tied—Maryland; five gave opposing majorities—Alabama, Georgia, Louisiana, North Carolina, Virginia; only two cast a solid vote in opposition—Mississippi and South Carolina.
These statistics did not indicate that "a few States were trying to force this amendment on a vast unwilling majority of States," as the opponents asserted. The increase from the majority of one in 1918 to 42 in 1919 is accounted for by the fact that at the congressional election during the interim 117 new members were elected, of whom 103 voted for the amendment. As it had been an issue in the campaign they represented the sentiment of their constituencies. Fifteen of the former members who were re-elected changed from negative to affirmative. From January, 1918, to June, 1919, not one member of either House broke his promise to vote for the amendment except Representative Daniel J. Riordan (Dem.) of New York, although many of them were subjected to extreme pressure by the interests opposed to it.
The resolution for the Amendment was introduced in the Senate May 23, 1919, by four members and half a dozen others expressed a wish to present it. The new Committee on Woman Suffrage had not been appointed and it was referred to the old one, whose chairman, Senator Jones, asked unanimous consent to have it placed on the calendar at once. Senators Underwood of Alabama; Hoke Smith of Georgia; Swanson of Virginia; Reed of Missouri, Democrats; Borah of Idaho; Wadsworth of New York, Republicans, and other opponents objected and it was delayed several days. Meanwhile a new committee was appointed with Senator James E. Watson (Rep.) of Indiana, as chairman. Finally on May 28 he was able to report the resolution favorably, by unanimous vote of the committee, and have it placed on the calendar for June 3.
The discussion was continued for two days, principally by the opposition, the friends of the amendment having agreed to consume no time except when necessary to correct misstatements. For this purpose Senators Lenroot of Wisconsin and Walsh of Montana, Republicans, and Thomas of Colorado, King of Utah, Kirby of Arkansas and Ashurst of Arizona, Democrats, made brief speeches. Senators Wadsworth, Brandegee (Rep.) of Connecticut and Borah; Underwood, Smith (Dem.) of South Carolina and Reed, consumed the rest of the time, Reed speaking several hours. Senator Underwood offered an amendment to have the ratifications by conventions instead of Legislatures, and Senator Phelan (Dem.) of California wanted to amend this by requiring them to be called the first week in December. Senator Harrison (Dem.) of Mississippi tried to have the word "white" inserted in the original amendment. Senator Gay (Dem.) of Louisiana wished to amend by providing that the States instead of the Congress should have power to enforce it. All these amendments were defeated by large majorities.
The Senators knew that all this debate was a waste of time, as enough votes were pledged to pass the amendment. Senator Watson opened and closed it in a dozen sentences. The roll was called at 5 p. m. June 4, and the vote was announced, 56 ayes, 25 noes. With the "pairs" that had been arranged the entire 96 members of the Senate were recorded and they stood as follows:
| Ayes | Noes | |
| Republicans | 40 | 9 |
| Democrats | 26 | 21 |
| Total | 66 | 30 |
The certificate to be sent to the Legislatures for ratification was signed by President of the Senate Thomas R. Marshall (Ind.) and Speaker of the House Frederick H. Gillett (Mass.) both unyielding opponents of the amendment.