The problem of the growing participation of labor unions and organizations in campaign activities did not disappear after the implementation of the Hatch Act. Additionally, several strikes organized by the labor movement proved an effective tool in making labor leaders important actors in the political process. In order to limit their political power, in 1943 Congress passed the War Labor Disputes Act (or Smith-Connally Act). It was adopted over the veto of President Franklin D. Roosevelt, whose New Deal policies were backed by the representatives of the labor unions.

According to the most important provision of the Smith-Connally Act, the president was granted the power to seize industrial war plants if organized strikes endangered the war industry. From the perspective of campaign finance restrictions, labor unions were prohibited from contributing to federal election campaigns in the same manner as the Tillman Act banned banks and corporations. But the effectiveness of the bill was only temporary – it expired after the end of World War II, leaving the regulation of the problem of campaign contributions by labor unions to the next Congress.

An Act relating to the use and operation by the United States of certain plants, mines, and facilities in the prosecution of war, and preventing strikes, lock-outs, and stoppages of production, and for other purposes…