POLITICIANS come and go. Whether Democrat or Republican, they tend to get corralled toward the middle after they are elected. No one expects them to keep their promises. Our divided form of government checks their ambitions.

I don’t even expect politicians to particularly respect the public or the U.S. Constitution, since both represent a hindrance to their exercise of power. But it does trouble me when they take aim at the First Amendment, which is the foundation of any freedom we citizens still enjoy, and our ultimate check on tyranny.

It was troubling, for example, that John McCain championed a campaign “reform” bill that made it harder to criticize and challenge incumbent politicians. And Americans had reason to be concerned about Sarah Palin’s “theoretical” questions as a city councilor about removing books from the shelves of the public library in Wasilla, Alaska. If we are to have a free society, people in positions of power must demonstrate that they respect the dissemination of ideas and refrain from censoring those they do not like. (Though a phony list of “banned books” made the rounds over the Internet, it seems that no books were actually removed.)

But those may pale beside the tactics of Sen. Barack Obama, who seems to be using intimidation and even the power of the state to stifle a vigorous debate about his background and beliefs. He should realize that such tactics tarnish his image as a decent and moderate man and raise concerns about whether he might be tempted to abuse his greater power as president.

In Democratic St. Louis, law-enforcement authorities calling themselves a “Truth Squad” — including a county circuit attorney, a city circuit attorney and a local sheriff — warned that those who criticized Senator Obama during the waning weeks of the campaign would face the risk of criminal libel charges if officials deemed their criticism was false.

While such charges could never hold up in court under the First Amendment, the strong-arm tactics might intimidate citizens who do not want to run the risk of an indictment and costly legal fees.

The outgoing governor of Missouri, Republican Matt Blunt, took the strategy seriously enough to issue a harshly worded statement denouncing what he called “the stench of police-state tactics” in the campaign.

“What Senator Obama and his helpers are doing is scandalous beyond words. The party that claims to be the party of Thomas Jefferson is abusing the justice system and offices of public trust to silence political criticism with threats of prosecution and criminal punishment,” he said.

The only purpose of such threats, he said, “is to frighten people away from expressing themselves, to chill free and open debate, to suppress support and donations to conservative organizations targeted by this anti-civil rights [approach], to strangle criticism of Mr. Obama, to suppress ads about his support of higher taxes, and to choke out criticism on television, radio, the Internet, blogs, e-mail and daily conversation about the election.”

Perhaps this is merely the work of overzealous supporters. But there have been other cases of the Obama campaign’s attempts to stifle debate. When a Chicago radio station invited journalist Stanley Kurtz to discuss his investigations of Mr. Obama’s work with the Chicago Annenberg Challenge, the Obama campaign issued an “Internet action alert,” and activists clogged the station’s telephone lines and swamped it with criticism for letting Mr. Kurtz appear.

In Pennsylvania, the Obama campaign lawyers sent “cease and desist” letters to TV stations for running an ad criticizing the senator’s record on gun control.

Senator Obama himself, in urging his supporters to talk to their neighbors, said, “I want you to argue with them and get in their face.”

From my perspective, there is too little arguing in public discourse these days, and too much getting in your face. Whether the Internet or some other phenomenon is to blame, people increasingly seem to wish to replace reasoned discourse with personal smears, threats and outright attempts to destroy others for daring to disagree. We seem to be losing our respect for the other guy’s right to an opinion and to disseminate ideas that can then be challenged.

America’s greatness owes everything to our tolerance for ideas — including those ideas we find repugnant. The way to defeat bad ideas is to drive them out with better ones — not to ban them, shout them down or scare opponents into silence.

Lawyers and prosecutors cannot sue and indict their way to a world in which no politicians lie. All they will do is trash the First Amendment and chill the speech of citizens who lack the means to fight back.

The great journalist H.L. Mencken, in enunciating his personal credo, wrote, “I believe in the complete freedom of thought and speech — alike for the humblest man and the mightiest. . . . But the whole thing, after all, may be put very simply. I believe that it is better to tell the truth than to lie. I believe that it is better to be free than to be a slave. And I believe that it is better to know than be ignorant.”

Many Americans believe this, and many have died protecting our freedom to disagree. The public should see to it, through pressure and the ballot box, that the politicians and their campaigns respect those basic rights as well.

Edward Achorn is The Journal’s deputy editorial-pages editor ( eachorn@projo.com).