In the presidential election of 1912, progressive Republican incumbent William Howard Taft sought reelection. Former progressive Republican president Teddy Roosevelt, dissatisfied with Taft's performance, ran for the Bull Moose Party. The split between the Republicans allowed Woodrow Wilson, who also ran as a progressive, to win the presidency for the Democrats.
In his second term. Wilson reluctantly led the country into World War I, but at the end of that war led in the creation of the League of Nations, an international organization conceptualized to help prevent world war. War had become too terrible to countenance.
Republicans controlled the White House from 1923 to 1933, the Senate from 1919 to 1931 and the House of Representatives from 1917 to 1933. Conservatives in the Congress voted against the Treaty of Versailles (which formally ended World War I) and voted against the United States joining the League of Nations.
What Difference Did it Make?
Understanding what would have been had history been different is always dangerous. The State Department writes:
Most historians hold that the League operated much less effectively without U.S. participation than it would have otherwise. However, even while rejecting membership, the Republican Presidents of the period, and their foreign policy architects, agreed with many of its goals. To the extent that Congress allowed, the Harding, Coolidge, and Hoover administrations associated the United States with League efforts on several issues. Constant suspicion in Congress, however, that steady U.S. cooperation with the League would lead to de facto membership prevented a close relationship between Washington and Geneva. Additionally, growing disillusionment with the Treaty of Versailles diminished support for the League in the United States and the international community. Wilson’s insistence that the Covenant be linked to the Treaty was a blunder; over time, the Treaty was discredited as unenforceable, short-sighted, or too extreme in its provisions, and the League’s failure either to enforce or revise it only reinforced U.S. congressional opposition to working with the League under any circumstances.The isolationism that dominated legislative thinking for much of the time between the wars seems now to have failed to recognize the international role that would be thrust upon the United States and to have contributed to the buildup towards World War II.
It is very important for members of Congress to recognize that they may be wrong in their beliefs and to grant respect to the executive branch views. This is perhaps especially important during the long election season, now at least two years, in which politicians are prone to make statements for political benefit that might not be in the country's best interest.