  Labor unions' greatest potential for political influence likely arises from
their direct connection to millions of individuals at the workplace. There,
they may change the ideological positions of both unionizing workers and their
non-unionizing management. In this paper, we analyze the workplace-level impact
of unionization on workers' and managers' political campaign contributions over
the 1980-2016 period in the United States. To do so, we link
establishment-level union election data with transaction-level campaign
contributions to federal and local candidates. In a difference-in-differences
design that we validate with regression discontinuity tests and a novel
instrumental variables approach, we find that unionization leads to a leftward
shift of campaign contributions. Unionization increases the support for
Democrats relative to Republicans not only among workers but also among
managers, which speaks against an increase in political cleavages between the
two groups. We provide evidence that our results are not driven by
compositional changes of the workforce and are weaker in states with
Right-to-Work laws where unions can invest fewer resources in political
activities.
