Conspiracy theory! Quick, what goes through your mind?

That LBJ was behind JFK’s assassination, at the behest of Texas oilmen?

That Princess Diana was actually murdered by the Queen, and Charles was in on it too?

That Woodward and Bernstein made up “Deep Throat”?

That’s what “conspiracy theory” used to call to mind: something so outlandish that no serious person would believe it to be true.

But lately, the term has been hijacked. A range of commentators has been using the phrase to confer instant illegitimacy on any argument with which they disagree. Want to close off the terms of the debate? Call something a conspiracy theory.

Exhibit A comes from Gregg Easterbrook. Writing last Wednesday in his blog for The New Republic, Easterbrook quotes Howard Dean telling Larry King why his candidacy has been slipping lately: “Because the establishment in Washington really realized that I might be the nominee and they did not like that. The media folks didn’t like it, the other folks in the race didn’t like it, and they did everything they could to make sure we weren’t [successful].”

According to Easterbrook, “This is a fairly loopy conspiracy theory,” — an attention-grabbing turn of phrase which TNR editors used as the headline for the post. Easterbrook continues:

The big change since about the time of the Gore endorsement is that voters have begun to speak. Rightly or wrongly, voters are choosing Kerry and Edwards. Before actual voting began, Dean’s campaign was all ephemera — polls, media attention, Internet action. Then voters weighed in, and the voters are picking someone else. Does Howard Dean seriously believe that “the establishment in Washington” somehow secretly controls the way people vote? If so let’s hear the evidence, please.

So is this really “a loopy conspiracy theory”? Let’s take Dean’s claims one-by-one:

Claim One: “Because the establishment in Washington really realized that I might be the nominee and they did not like that.”

First, there’s little debate over the fact that many powerful Democrats in Washington were deeply worried about the prospect of Dean winning the nomination. So does Easterbrook seriously believe that these Democratic power-brokers have no means of affecting the race? That they play no role in helping particular candidates to build a campaign staff? That they’re unable to help line up support from local elected officials, party activists, and labor unions that can help get out the vote on election day? If they’re really as powerless as Easterbrook seems to think, what do these people do all day?

No one is suggesting that “‘the establishment in Washington’ somehow secretly controls the way people vote.” But Dean is suggesting that powerful Washington-based Democrats wield some influence in determining their party’s nominee, and that they used that influence to counter him. That seems to us like a plausible contention.

And Dean’s thesis that he’s never exactly been flavor of the month among Washington Democrats doesn’t seem like a “conspiracy theory” to The Wall Street Journal. On Thursday, John Harwood, Jeanne Cummings, and Jacob Schlesinger wrote, “The race has matched Democratic party leaders’ hopes in some ways. The candidate whom party strategists feared might be a big November loser, Mr. Dean, has tumbled from front-runner to desperate also-ran.” (subscription required for link)

Claim Two: “The media folks didn’t like it … and they did everything they could to make sure we weren’t [successful].”

This is a harder charge to back up. Protestations of bias from the Dean camp not-withstanding, there’s no solid evidence that “the media folks” prefer one candidate to another. But after even Diane Sawyer — along with executives from all the major networks save NBC — admitted that the media had treated Dean unfairly by overplaying his now-notorious Iowa concession speech, calling Dean’s claim of media bias a “loopy conspiracy theory” seems like a stretch.

Claim Three: “The other folks in the race didn’t like it, and they did everything they could to make sure we weren’t [successful].”

Unless Easterbrook wants to argue that Dean’s rivals actually have actually been rooting for him all along — which would make Easterbrook the conspiracy theorist — this is no “loopy conspiracy theory.”

Let’s be clear: Easterbrook has every right to be unconvinced by Dean’s charge that the Washington establishment and the media contributed to his downfall. But whether one agrees with it or not, Dean’s argument is a serious claim that deserves to be taken seriously. By labeling it a “conspiracy theory,” Easterbrook dismisses a relatively complex argument, on which fair-minded people might disagree, in a mere paragraph. The biggest loser is the quality of the public debate.

Zachary Roth is a contributing editor to The Washington Monthly. He also has written for The Los Angeles Times, The New Republic, Slate, Salon, The Daily Beast, and Talking Points Memo, among other outlets.