The professional Left is having a good laugh about the conspiracy theories swirling around Jade Helm 15, a military training exercise taking place across the American Southwest. The knuckle-draggers on the Right have evidently concocted some fantasy in which the federal government uses its military power as — stop me if you’ve heard this one before — a tool of domestic tyranny! Jon Stewart, Rachel Maddow, et al. are having a field day.

According to the New York Times, the idea that Jade Helm 15 is part of a secret plan to impose martial law represents “the outer edges of political paranoia.” Perhaps, but those outer edges are more often occupied by leftwing fantasists than Tea Party activists. In 2007, for example, when Congress granted the president expanded powers to federalize the National Guard (in response to Louisiana Governor Kathleen Blanco’s refusal to cede control of the Guard during Hurricane Katrina), progressives howled that tyranny was just around the corner. Patrick Leahy, the famously progressive senator from Vermont, objected that “the last thing we need is to make it easier for presidents to declare martial law.” The Daily Kos warned: “Congress is voting on whether to give Bush more power to invoke martial law. This is huge.” And yet, now the Daily Kos says that the Jade Helm martial law conspiracy is “the single stupidest thing to come out of Texas.”

The fear of a reactionary president imposing martial law goes way back on the left—at least to the 1980s. In 1987, the Miami Herald reported that the Reagan Administration had a secret plan to declare martial law in the event of a perceived emergency, including “national opposition to a US military invasion abroad.” Although this secret plan was never confirmed, a 1996 book written by a progressive academic, Christian Smith, and published by the University of Chicago Press, states that “evidence strongly suggests that in 1984, the [National Security Council] and FEMA collaborated in designing a top-secret contingency plan, named Rex 84, to suspend the US Constitution, declare martial law, appoint military commanders to run state and local governments, and detain masses of people considered to be national security threats.”