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Employers also seek to influence their employees’ support for candidates or issues within the workplace, sometimes through coercion or manipulation. Employers have outright fired workers for their political bumper stickers. Others have tried to change their workers’ minds; for example, the CEO of the time-share company Westgate Resorts sent his 7,000 employees an email predicting layoffs and benefit cuts if President Barack Obama was reelected in 2012. Was he serious? Apparently not, but it is easy to imagine workers thinking otherwise when casting their ballots.

Federal law has very little to say about employers who exert these kinds of pressures at work; for example, no federal law prohibits private-sector employment discrimination based on political viewpoints. Some state and local laws pick up part of the slack, but they tend to be limited to the most coercive employment practices, such as threatening to fire employees because they expressed support for a particular candidate.

One reason legislatures do not do more is the First Amendment—specifically, the Supreme Court’s robust protection for corporate political advocacy. In 2010, five conservative justices agreed in Citizens United v. FEC that “if the First Amendment has any force, it prohibits Congress from fining or jailing citizens, or associations of citizens, for simply engaging in political speech.” That lofty language translates to a First Amendment right for corporations to spend unlimited general treasury funds on political advocacy. It also means that a law targeting employers’ noncoercive attempts to influence their employees’ politics would face an uphill climb.

Although Citizens United applies to unions as well as corporations, unions may not require represented workers to contribute to their political advocacy. No equivalent funding limitation applies to corporations; for example, shareholders cannot opt out of a corporation’s political spending.

Read: How to reverse Citizens United

A combination of lack of political will and the First Amendment means that we are unlikely to see more robust legislative responses to reduce employers’ political influence. But some unionized employees are better positioned than others to resist pressure.

First, union contracts tend to bring better job security; for example, most contain “just cause” provisions, which mean employees can’t be fired without a good reason. To state the obvious, “I didn’t like their political bumper sticker” and “They didn’t promise to vote for my candidate” are not good reasons.

Second, unions can talk politics with workers—though they cannot visit employment consequences on those who decline to engage—potentially offering a point of view that is different than that of the employer. Unions often also encourage their members to vote and get involved in politics in other ways; one study found that “union members, particularly those without any college education, are significantly more politically knowledgeable than their non-union counterparts.”