A high-profile successful strike by one group of workers, in turn, encourages other workers to take the risk. “When, say, teachers in Oklahoma see their West Virginia colleagues walking out and winning substantial pay increases, there is a contagion effect,” as Jake Rosenfeld, a professor at Washington University in St. Louis, has said. “They start to believe, ‘Hey, we can do that, too.’”

Over most of the past 40 years, of course, the dynamic has been working in the opposite direction. President Ronald Reagan famously fired striking air traffic controllers in 1981 , which encouraged companies to play hardball with their own workers. As more companies did so — refusing to grant raises and firing strikers — workers became afraid and disillusioned.

For years, the United Automobile Workers union — the one that went on strike this week — has been suffering from this kind of vicious cycle.

Some of its problems have been self-inflicted, including corruption. U.A.W. leaders have recently been the subject of a corruption investigation, in which a few have been convicted of accepting bribes. In some cases, they took the bribes from employers in exchange for accepting concessions during contract talks. When the U.A.W. narrowly lost an election to unionize workers at a Volkswagen plant in Tennessee this year, some workers said — understandably — that they voted against it because they were skeptical the union would really fight for their interests.

The G.M. strike is in part an effort by the union to halt this cycle of defeat. By calling the strike, the union’s remaining leaders are trying to demonstrate a new willingness to fight for their members. “A successful strike at General Motors could persuade U.A.W. members that the union is willing to take significant risks to fight on behalf of its members, potentially opening the door to more organizing in the anti-union South, where many auto plants have migrated,” Mike Elk wrote in The American Prospect yesterday.