Senator Joseph Lieberman was once thought merely to be to the right of his erstwhile colleagues in the Democratic Party. These days, it sounds like the independent Senator from Connecticut is to the right of most Republicans, including the President himself—especially when it comes to foreign affairs.

Mr. Lieberman appeared on Face the Nation on Sunday, apparently with the primary purpose of rattling a saber in Iran’s direction.

“If there’s any hope of the Iranians living according to the international rule of law … we can’t just talk to them. If they don’t play by the rules, we’ve got to use our force and, to me, that would include military action,” he told Bob Schieffer.

The concept of taking military action against a nation of Iran’s size and capabilities, while the U.S. remains bogged down next-door in Iraq, seems impractical, if not crazy.

Mr. Lieberman, however, has always been an optimist where military force is concerned—witness, for example, his consistently sunny assessments of the situation in Iraq.

The Senator asserted that “we have good evidence” that Iran has a camp at which people are trained to attack U.S. forces in Iraq. A single “strike” could sort the problem out, he suggested, adding that “I think you could probably do a lot of it from the air.”

Sunday’s performance was not the first time that Mr. Lieberman has made hawkish noises about Iran.

“While we are naturally focused on Iraq, a larger war is emerging,” he wrote in a Washington Post op-ed in December. “On one side are extremists and terrorists led and sponsored by Iran, on the other moderates and democrats supported by the United States.”

Mr. Lieberman also suggested that Al Qaeda and the Iranian government were pursuing a joint strategy in Iraq—an assertion that many observers viewed with considerable skepticism, given that Shiite Iran seems to have a greater vested interest in backing forces from its own strand of Islam than in supporting the Sunni militants of Al Qaeda.

And back in April 2006, Mr. Lieberman gave an interview to The Jerusalem Post in which he held out the possibility of U.S. strikes against Iranian nuclear facilities.

Mr. Lieberman’s hard-line approach may be rooted in justifiable concerns about Iran’s intentions. But the solution he suggested on Sunday is a recipe for disaster. It incorporates the same ingredients of hubris, wishful thinking and over-simplification that have cost the U.S. so dear in Iraq.

During his Jerusalem Post interview of 14 months ago, Mr. Lieberman at least mentioned the need “to encourage the reformist and opposition elements in Iran.” What would become of this idea, were the U.S. to bomb Iran?

To imagine that the Iranian people would react to an American attack with anything other than anger and a reflexive patriotism—both of which would likely benefit President Mahmoud Ahmadinejad—flies in the face of all evidence.

American “encouragement” of Iranian reformists is a delicate issue at the best of times. This reporter, visiting Tehran last month, was struck by the degree to which even the harshest critics of Mr. Ahmadinejad were equally strident in their determination that the U.S. should keep its nose out of Iranian affairs.

And public opinion aside, the logistics of Mr. Lieberman’s plan are dubious. His notion of a single air strike to resolve the problem of alleged Iranian training of insurgents seems fanciful. Even if the accusation is true, presumably the Iranians could simply set up another facility elsewhere.

Perhaps the Connecticut Senator believes a one-shot approach would intimidate the Iranians out of further misbehavior.

But would Tehran be easily cowed, given its awareness of the U.S.’ plummeting stock in the region and the strain imposed on the American military by wars in Iraq and Afghanistan? It seems at least an even bet that the Iranian response would be to strike back hard.

Mr. Lieberman seems to be falling into an old trap: the belief that superior military firepower can smoothly wipe out shadowy threats while carrying no adverse political consequences. The shortcomings of such an approach have been shown in the grisliest way to the U.S. in Iraq and to its ally Israel during last year’s disastrous incursion into Lebanon.

None of this is to deny that Iran is a threat to the U.S., to Israel and to the Middle East as a whole. The question is how that threat should be counteracted.

On Monday, the Democratic leader in the Senate, Harry Reid, told ThinkProgress.org, “I believe our efforts should be diplomatic in nature …. I know Joe means well, but I don’t agree with him.”

The previous day on Meet the Press, former Secretary of State Colin Powell said, “I think we should be talking to Iran, we should be talking to Syria. Not to solve a particular problem or crisis … but just to have dialogue with people who are involved in this region in so many ways.”

Dialogue and diplomacy do not make for especially magnetic rallying calls. But they are a much more sensible idea than the dangerous chimera of a short sharp shock to Iran proposed by Mr. Lieberman.