Recently William Cronon, a historian who teaches at the University of Wisconsin, decided to weigh in on his state’s political turmoil. He started a blog, “Scholar as Citizen,” devoting his first post to the role of the shadowy American Legislative Exchange Council in pushing hard-line conservative legislation at the state level. Then he published an opinion piece in The Times, suggesting that Wisconsin’s Republican governor has turned his back on the state’s long tradition of “neighborliness, decency and mutual respect.”

So what was the G.O.P.’s response? A demand for copies of all e-mails sent to or from Mr. Cronon’s university mail account containing any of a wide range of terms, including the word “Republican” and the names of a number of Republican politicians.

If this action strikes you as no big deal, you’re missing the point. The hard right — which these days is more or less synonymous with the Republican Party — has a modus operandi when it comes to scholars expressing views it dislikes: never mind the substance, go for the smear. And that demand for copies of e-mails is obviously motivated by no more than a hope that it will provide something, anything, that can be used to subject Mr. Cronon to the usual treatment.

The Cronon affair, then, is one more indicator of just how reflexively vindictive, how un-American, one of our two great political parties has become.