It's tough trying to please people who crave vengeance almost as much as Madame Defarge, the unsparing French revolutionary in Dickens' "Tale of Two Cities." That's what Barack Obama found out last week -- and will find out next week and for weeks to come unless he settles once and for all that he will follow the practice of all his predecessors and not prosecute decision-makers in the previous administration.

The Madame Defarges of the Democratic left want to see the guillotine flash down and heads roll. Specifically, they want to see the prosecution or impeachment of officials who approved enhanced interrogation techniques -- torture, in their view.

The president, it appears, is of two minds. On April 16, he released memorandums from the Bush administration Office of Legal Counsel approving the interrogation methods and said that CIA interrogators relying on them would not be prosecuted. Also released was the partial text of a letter from Director of National Intelligence Dennis Blair characterizing those memos as "graphic and disturbing."

Obama was criticized for revealing intelligence information useful to our enemies. "Nobody should pretend," wrote Washington Post columnist David Ignatius, who approved of Obama's decision, "that the disclosures weren't costly to CIA morale and effectiveness."

On April 20, Obama journeyed to CIA headquarters and defended his decisions. But the Madame Defarges had their knitting needles out, hauling in petitions with 250,000 signatures and demanding blood. On April 21, Obama caved, saying that Bush administration officials who approved the methods could be prosecuted if the attorney general wanted to press the cases. He didn't give the Madame Defarges all they wanted, resisting Speaker Nancy Pelosi's call for a 9/11-type commission.

It is an article of faith among the Madame Defarges that the interrogation techniques they consider torture didn't produce useful information. All along Obama tried to pay homage to this dogma.

The text of Blair's letter released to the public carefully omitted his admission that "high value information came from interrogations in which the methods were used." Just normal editing, said his spokesman. Yeah, sure. Nor has Obama showed any sign of agreeing to Dick Cheney's demand that the full results of the interrogations should be released. That might embarrass the Madame Defarges.

Whence cometh the fury of these people? I think it arises less from revulsion at interrogation techniques -- who thinks that captured al-Qaida leaders should be treated politely and will then tell the full truth? -- than it does from a desire to see George W. Bush and Bush administration officials publicly humiliated and repudiated. Just as Madame Defarge relished watching the condemned walk from the tumbrel to the guillotine, our contemporary Defarges want to see the people they hate condemned and destroyed.

It doesn't seem to matter to our Madame Defarges that it's not clear that Bush officials violated any criminal law. One of the core principles of our law is that criminal statutes must be construed strictly against the government. If the government wants to deprive someone of his liberty for doing something, it should be very specific about what that something is. This distinguishes our system from authoritarian and totalitarian regimes that demand, like Alice's Red Queen, "verdict first, trial later."

It also doesn't occur to the Madame Defarges of our times that revolutions like hers tend to devour their own. Robespierre followed Marie Antoinette to the guillotine not so many months later. Today we see Pelosi trying to explain how she was present at confidential briefings where the enhanced interrogation methods were described and did nothing to stop them from being applied.

If there is going to be a "truth commission" -- a title that is redolent of Stalinist purges -- shouldn't she be one of the first to testify? As for Barack Obama, asked in a September 2007 if we should "beat out of" an al-Qaida higher-up details of an impending attack, he said "there are going to be all sorts of hypotheticals, an emergency situation, and I will make that judgment at that time." So "torture" just might be OK under the right circumstances.

In the meantime, Obama's appeasement of the Madame Defarges carries a political price. Pollster Scott Rasmussen reports that 58 percent of Americans believe his release of the CIA memos endangers national security. Show trials of Bush administration officials could raise that number. Appeasing the Madame Defarges may cost more than it is worth.