His loyal aides say, “Bill Frist will be back,” but that’s the kind of thing congressional staffers always say when their boss prematurely reaches the end of his political career, as Mr. Frist did last week. Roughly translated, it means: “Someday Bwana will return, and when he does we will once again have important jobs and excellent parking spaces.”

I wouldn’t bet on it. The Senate majority leader, who had declined to run for another term as senator from Tennessee this year, announced that he won’t run for president in 2008 either. It’s no great loss for Republicans, and Republicans, surprisingly, seem to know it.

Yet it’s a curious development all the same. As recently as a year ago, Washington soothsayers were placing Mr. Frist in the bottom of the first tier — or was it the top of the second tier? — of possible Republican presidential candidates.

Senator Frist seemed ideal. He’s well-spoken and presentable — nice looking but, as befits a Republican, not too nice looking.

He’s from a Southern state that’s not excessively Southern: Tennessee is no Alabama. He’s conservative, sort of, but a self-described “compassionate conservative,” which is to say, not very.

Most important, he’s a heart surgeon by trade, one of those rare politicians who could claim a life of accomplishment beyond politics, which, paradoxically, made him all the more appealing politically. To drive the point home, Senator Frist had the senatorial nameplate outside his office recast to identify him as “M.D.”

Mr. Frist appeared to be what voters always say they want: a nonpolitician politician.

And now his removal from the presidential campaign has been greeted with shrugs and ho-hums. The Frist phenom turned out to be a mirage, and when it went poof it illuminated some important things about the demands and expectations of American politics.

Senator Frist was handpicked in 2003 to be Senate majority leader by the Bush administration, presumably by President Bush himself along with his top political swami, Karl Rove. The similarities in personal backgrounds — both Messrs. Bush and Frist are wealthy patricians from the New South — might have accounted for the attraction.

Mr. Frist’s friends and defenders say that the position President Bush placed him in, as chief water carrier for the domestic agenda of an administration that didn’t have much of a domestic agenda, could never show Mr. Frist to his best advantage. It left him no room, they say, to demonstrate the strength, conviction, and independence that voters claim to like in a politician.

But even when Mr. Frist tried to assert himself independently of the White House, he seemed ill-suited to the political tasks he had sought. After an initial (and fiscally dubious) success in shepherding the Medicare prescription drug benefit through the Senate, Mr. Frist proved incapable of prying loose such major legislative packages as the energy bill or tort reform.

Democratic efforts to filibuster President Bush’s judicial nominees were only overcome by the unimaginatively named “Gang of 14,” who presented their compromise to Mr. Frist as a fait accompli.

Then, last summer, for reasons never entirely clear, gas prices were suddenly deemed by Washington to be intolerably high, and Mr. Frist joined the hysteria and doubled it.

After a quick brainstorming session he presented his solution: a $100 check issued to every American taxpayer whether or not they drove a car. The proposal combined the economic philosophy of Jimmy Carter with the political dexterity of, well, Jimmy Carter.

The image of clumsiness was reinforced by Mr. Frist’s behavior on the morally fraught issue of federal funding for embryonic stem-cell research. Once a supporter of Mr. Bush’s ban on funding, Mr. Frist revised his position in a much-heralded speech last year.

Americans generally entertain an unrealistically high opinion of doctors, as they do of all specialists, and Mr. Frist’s medical degree, in the eyes of some columnists and colleagues, somehow bestowed upon him an oracular power to pronounce on the stem-cell issue, never mind that the questions raised by federal funding are not medical but moral and political.

Mr. Frist’s speech was a masterpiece of confusion. He opened it by declaring himself to be “pro-life” and asserting his belief that embryos constitute inviolable human life. Then he went on to advocate spending federal money to harvest those embryos so their parts could be used in medical research.

Worse, Mr. Frist’s confusion seemed not just intellectual but political, a clumsy pander. It was as though he had delivered two speeches: one to mollify the Republican Party’s pro-life voters, another to score points with moderates and to earn the gratitude of the biotechnology fundraising apparatus. In the end, none of these constituencies was impressed or appeased.

Edmund Burke, the 18th-century British philosopher, once expressed alarm at the large number of doctors elected to the French Assembly. Medical men, he said, were ill-equipped for politics, which Burke always considered an elevated profession requiring both principles and skill.

“The sides of sickbeds are not the academies for forming statesmen and legislators,” Burke wrote.

The fall of Bill Frist bears him out. The paradox of nonpol politicians is that, while they may seem more appealing than the professional kind, they aren’t nearly as good at politics, and politics, for better or worse, is what we elect politicians to do.

It turns out that politicians make the best politicians. Who would have guessed?

Mr. Ferguson is a columnist for Bloomberg News.