Woodrow Wilson chose to make support for his peace plans a political issue in the Congressional elections of 1918. The president felt that strong support from Congress, particularly the Senate, would be an important means to increase his bargaining muscle with the European powers in the coming negotiations.
In late October, Wilson issued the following appeal to the voters:
If you have approved of my leadership and want me to continue to be your unembarrassed spokesman in affairs at home and abroad, I earnestly beg that you will express yourselves unmistakably to that effect by returning a Democratic majority to both the Senate and the House of Representatives.
Republicans were understandably angry. They had willingly participated in an informal political truce during the fighting and had actually been more supportive of Wilson’s war plans than his own party. His blatantly partisan appeal helped to reignite political bickering in Congress and succeeded in offending many in the general public as well.
Wilson had enjoyed Democratic majorities in both houses of Congress since his first election in 1912. On November 5, 1918, however, the voters spurned the president’s appeal and gave the Republicans an impressive 50-seat majority in the House and a narrow two-seat edge in the Senate.
It is not unusual for administrations to lose congressional seats in midterm elections and Wilson’s appeal may have prevented even greater losses than those that occurred on Election Day. However, Wilson probably should have heeded the advice of those who had urged him to ask the voters to return supporters of his peace plan from both parties.
See specific information regarding party representation in the Composition of Congress under Wilson.
See also Wilson's Search for Peace.