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.

The demand for Mr. Cronon’s correspondence has obvious parallels with the ongoing smear campaign against climate science and climate scientists, which has lately relied heavily on supposedly damaging quotations found in e-mail records.

Back in 2009 climate skeptics got hold of more than a thousand e-mails between researchers at the Climate Research Unit at Britain’s University of East Anglia. Nothing in the correspondence suggested any kind of scientific impropriety; at most, we learned — I know this will shock you — that scientists are human beings, who occasionally say snide things about people they dislike.

But that didn’t stop the usual suspects from proclaiming that they had uncovered “Climategate,” a scientific scandal that somehow invalidates the vast array of evidence for man-made climate change. And this fake scandal gives an indication of what the Wisconsin G.O.P. presumably hopes to do to Mr. Cronon.

After all, if you go through a large number of messages looking for lines that can be made to sound bad, you’re bound to find a few. In fact, it’s surprising how few such lines the critics managed to find in the “Climategate” trove: much of the smear has focused on just one e-mail, in which a researcher talks about using a “trick” to “hide the decline” in a particular series. In context, it’s clear that he’s talking about making an effective graphical presentation, not about suppressing evidence. But the right wants a scandal, and won’t take no for an answer.

Is there any doubt that Wisconsin Republicans are hoping for a similar “success” against Mr. Cronon?

Now, in this case they’ll probably come up dry. Mr. Cronon writes on his blog that he has been careful never to use his university e-mail for personal business, exhibiting a scrupulousness that’s neither common nor expected in the academic world. (Full disclosure: I have, at times, used my university e-mail to remind my wife to feed the cats, confirm dinner plans with friends, etc.)

Beyond that, Mr. Cronon — the president-elect of the American Historical Association — has a secure reputation as a towering figure in his field. His magnificent “Nature’s Metropolis: Chicago and the Great West” is the best work of economic and business history I’ve ever read — and I read a lot of that kind of thing.

So we don’t need to worry about Mr. Cronon — but we should worry a lot about the wider effect of attacks like the one he’s facing.

Legally, Republicans may be within their rights: Wisconsin’s open records law provides public access to e-mails of government employees, although the law was clearly intended to apply to state officials, not university professors. But there’s a clear chilling effect when scholars know that they may face witch hunts whenever they say things the G.O.P. doesn’t like.

Someone like Mr. Cronon can stand up to the pressure. But less eminent and established researchers won’t just become reluctant to act as concerned citizens, weighing in on current debates; they’ll be deterred from even doing research on topics that might get them in trouble.

What’s at stake here, in other words, is whether we’re going to have an open national discourse in which scholars feel free to go wherever the evidence takes them, and to contribute to public understanding. Republicans, in Wisconsin and elsewhere, are trying to shut that kind of discourse down. It’s up to the rest of us to see that they don’t succeed.