As the 2008 general election heats up, one of John McCain’s strongest political advantages is his opponent Barack Obama’s lack of political experience. No surprise there: when Mr. McCain began his political career, Mr. Obama was still a college student.

But lately, Mr. McCain seems to be taking the experience argument in an extreme direction: intimating that Mr. Obama doesn’t actually know, well, much of anything.

Here, for example, is Mr. McCain in a recent op-ed in The Detroit Free Press: “Those who would lead our countries must work to ensure that the benefits of NAFTA are understood throughout our countries, and not jeopardized through cowboy diplomacy. U.S. Sen. Barack Obama does not understand this.”

Or how about the recent Supreme Court decision on granting the right of habeas corpus to Guantanamo detainees: “Senator Obama is obviously confused about what the United States Supreme Court decided and what he is calling for,” Mr. McCain said in a blog entry posted on June 19.

On the recently proposed extension of the G.I. Bill, the McCain campaign issued a statement blasting Senator Obama for failing to “take the time and trouble to understand this issue.”

Or what about Mr. Obama’s knowledge of American foreign policy: He “either hasn’t read” or doesn’t understand “the history of this country in warfare, and the way that we secure alliances and secure the peace,” Mr. McCain said from his campaign plane in May.

Reading these comments, one can only wonder how Mr. Obama won the Democratic nomination!

Of course, this is smart politics for Mr. McCain. According to a recent Zogby poll, more than half of all Americans think Mr. Obama lacks the necessary experience to serve as president. The numbers are even more troubling among white voters. According to a Washington Post poll, about half of them think Mr. Obama would be a risky pick and only 43 percent think he has the experience needed for the nation’s highest office.

Mr. McCain’s ability to build on these poll numbers may be his best, and only, hope for victory in November. But there is a danger for Mr. McCain when he veers from questioning his opponent’s experience to questioning his intellect. Indeed, Mr. McCain’s recent comments verge into the realm of condescension toward the Democratic candidate and his supporters.

Mr. McCain would be wise to remember Al Gore’s sighing during the 2000 presidential debates or George H.W. Bush’s declaration in 1992 that “My dog Millie knows more about foreign affairs than these two bozos” in talking about the Democratic ticket. Voters didn’t exactly warm to these demeaning words.

What’s worse, by continually attacking Mr. Obama’s understanding of policy issues, John McCain runs the risk of actually helping the Democrat neutralize the experience issue. In 1980, supporters of President Jimmy Carter regularly intimated that Ronald Reagan was an intellectual lightweight not to mention a warmonger and a racist. But when the two men debated, and Americans saw that Reagan wasn’t the caricature that he was being presented as, poll numbers showed a huge shift toward the Republican. A similar phenomenon occurred in 2000 when skeptical Democrats set the bar so low for George W. Bush.

When Americans hear Mr. Obama in the presidential debates and realize that he does in fact understand many of the issues facing the country (or even worse that they agree with him), Mr. McCain’s attacks will ring hollow. Such a low threshold is being set for Mr. Obama that he will almost certainly top it and in the process pass the greatest test he will face from voters between now and November, namely, is he up to the job.

But there is another, even greater, risk. Mr. McCain’s constant undermining of Mr. Obama’s intelligence and judgment smacks of disrespect and even seems a bit curmudgeonly. And curmudgeonly is most certainly the one word that Mr. McCain would be wise to avoid in this election.