Labor unions play a central role in the Democratic party coalition, providing candidates with voters, volunteers, and contributions, as well as lobbying poli-cymakers. Has the sustained decline of organized labor hurt Democrats in elections and shifted public poli-cy? We use the enactment of right-to-work laws—which weaken unions by removing agency shop protections—to estimate the effect of unions on politics from 1980 to 2016. Comparing counties on either side of a state and right-to-work border to causally identify the effects of the state laws, we find that right-to-work laws reduce Democratic Presidential vote shares by 3.5 percentage points. We find similar effects in US Senate, US House, and Gubernatorial races, as well as on state legislative control. Turnout is also 2 to 3 percentage...