While the revelations made in this article are hardly a shock, understanding the role of the public sector unions in political donations is key to understanding the functioning of the modern American Left. The deep pockets of teachers unions and other public sector unions provide the financial infrastructure that keeps the Left in business.

It’s the ultimate political machine. Teachers’ unions lobby elected officials to get more money and benefits for their members. The voting clout that the unions have in state and local politics makes it easy for politicians to give them what they want—even if it is more than the city can actually afford. As a result, many cities are now struggling with high pension promises that they are in no position to keep. Many cities are now hoping to scale some of these pensions back, but the union machine continues to fight such measures even as the pensions become unsustainable. Many find that the unions are just too powerful to fight.

But this is only one side of the machine. With the dues money that they get, teachers unions and other public sector unions fund a large infrastructure of other, generally left-leaning, political groups. These groups help pressure politicians to give the unions the benefits and salary agreements they want, even in circumstances where this may be only tangential to the organization’s core mission. The unions’ pockets are deep, and union leaders often have the political savvy to use their funds to create a broader alliance to support their interests.