Astroturf, in the political sense, is thought to have been coined by Senator Lloyd Bentsen, who used it to describe the “mountain of cards and letters” he got promoting what he saw as the interests of insurance companies. “A fellow from Texas can tell the difference between grass roots and Astroturf,” Bentsen said in 1985, “this is generated mail.”

Generated mail is a pretty old idea. In Shakespeare’s “Julius Caesar,” Brutus is persuaded to assassinate Caesar in part by letters of support from the public — letters that were actually faked by Cassius “in several hands … as if they came from several citizens.”

More recently, a Washington lobbying firm working for the coal industry was caught sending bogus letters to members of Congress — supposedly from community organizations — urging them to oppose the House cap-and-trade bill. Such brazen fraud is rare, though, and politicians are usually pretty savvy about seeing through it. More effective are campaigns aimed at generating news coverage to convince people that many other people hold a certain position. This is what Republicans are now accused of doing. What’s unclear is how this differs from old-fashioned political organizing.