MEGAN MCARDLE: You Can’t Be Neutral in a Public-Sector Union.

When you’re negotiating with governments, there’s never a bright line where politics ends and negotiation begins. That’s why unions, and other folks who sell goods and services to governments, spend so much money on lobbying.

Large public-sector unions, like for police and sanitation workers, wield even more influence: Every time they sit down for negotiations, they bring the threat that their large and politically active membership will vote the bosses out of office if the talks go poorly. Public-sector workers are often legally forbidden the classic tools of labor organization, such as the walkout or the “work to rule” slowdown. But this Election Day cudgel is much bigger.

Often, of course, public workers’ unions augment this with political contributions and aggressive lobbying efforts, on topics that may go well beyond wages and benefits, and into political causes that help them build coalitions with other left-wing groups.

This broad political activity is part of why public-sector unions are doing so much better than their private-sector counterparts. But it also means that “closed shop” labor arrangements effectively force people into a package deal: Want to be a teacher or a cop? Then you have to join a union and make political statements that you may not agree with.

I agree with FDR: Public-sector unions are pernicious and should be banned.