Internal Democratic strains were exacerbated by an effort led by Roosevelt to purge certain conservative senators for defeat in Democratic primaries, including Walter George of Georgia, Millard Tydings of Maryland and Ellison Smith of South Carolina, along with the chairman of the House Rules Committee, John J. O'Connor of New York.

[2] While a number of New Deal supporters won primary elections, such as Sen. Alben Barkley in Kentucky, who defeated Happy Chandler, in Idaho, Sen. James P. Pope, a prominent New Deal supporter, lost his bid for re-nomination, as did California senator William McAdoo.

[3] Re-energized Republicans focused attention on strong fresh candidates in major states, especially Robert A. Taft, the conservative from Ohio,[4] Earl Warren (future Chief Justice), the moderate who won both the Republican and the Democratic primaries in California,[5] and Thomas Dewey, the crusading prosecutor from New York.

[6] The Republican resurgence in 1938 was made possible by carrying 50% of the vote outside the South, giving GOP leaders confidence it had a strong base for the 1940 presidential election.

Representatives Edward E. Cox, Howard W. Smith, and other Southern Democrats opposed Roosevelt's policies with the Republicans, but were in the minority.