So what will be left of the Republican Party after next week's US election? The answer lies in the sands of Florida, where the sunshine-state Republicans have nominated an unrepentant torturer as their candidate for Congress. They view his readiness to torture an innocent Iraqi not as a source of shame, but as his prime qualification for office. This is American conservatism in the dying days of Bush – and it points out the direction that Sarah Palin would like to take it in 2012.

In August 2003, Colonel Allen West – commanding a US unit in Baghdad – heard a rumour that one of the Iraqi policeman he was working with was a secret insurgent. He ordered his officers to go and seize Yehiya Hamoodi, a thin, bespectacled 31-year-old, from his home. They dragged him into a Humvee, beat him, and then handcuffed, shackled and blindfolded him. In a dank interrogation room, they told him he had better start talking.

Perplexed and terrified, Yehiya explained he didn't know what they were talking about: why was he here? So West was called in. He told Yehiya he was going to be killed. While his men beat him again, he explained he had one last chance to save his life – by talking.

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Yehiya protested: I am innocent! What are you talking about? So West took him outside, had him pinned down, and began to shoot. First he fired into the air. Then he ordered his men to ram Yehiya's head into a barrel used for cleaning weapons – and fired right next to his head. Then he began to count down from five. Finally Yehiya began to scream out names – any name he could think of, just to make it stop.

The men he named were seized and roughed up in turn. No evidence was found of any plot, and after another 45 days of terror, Yehiya was released. Today, he is severely traumatised, and collapses when he sees a Humvee approaching. The story only came to light after one of West's soldiers began to protest against these practices, and the Pentagon launched an investigation. At a pre-trial hearing, West was fined $5,000, and now concedes grudgingly: "It's possible I was wrong about Mr Hamoodi." But he says he would do it again, and again, and again.

West has even taken to joking about it, gaining applause for telling Republican audiences: "It wasn't torture. Seeing Rosie O'Donnell naked would be torture." But the 1994 Convention Against Torture, to which the US is a signatory, is explicit: "Threat of imminent death" is the third form of torture it outlaws. There are reams of studies showing it can traumatise a person for life.

Yet the Republican Party has rallied to the defence of this torturer, and of torture in general. The Bush administration has ordered the simulated drowning of "high-value" suspects, and set up secret black ops sites across the world where it is practiced. After Afghan detainees were hanged from the ceiling and beaten to death, the officers responsible were merely given a "letter of reprimand".

West's "toughness" is fawned over; one leading conservative magazine has even named him its Man of the Year. And Sarah Palin, the Party's darling, mocks Barack Obama's opposition to torture. She complains: "Al-Qaida terrorists still plot to inflict catastrophic harm on America [and] he's worried that someone won't read them their rights." Palin is fond of saying that she "won't blink when it comes to terror", but if you don't blink, your corneas dry out, and you go blind.

At first, the rise of John McCain looked like a repudiation of torture. McCain was tortured by the Viet Cong for three years, and the beatings were so vicious that even today he can't raise his arms to brush his own hair. For a time, he was a loud, proud opponent of torture – but then he caved. In February 2008, he voted to allow the CIA to be excluded from the ban on torture – when he knows the CIA who are the prime American torturers today.

Then, when the Supreme Court ruled that Guantanamo detainees have basic habeas corpus rights, McCain called it "one of the worst decisions in the history of the country." If McCain will compromise on this, he will compromise on anything. He has tried to flip-flop back, saying he would ban torture after all, but if he tried now, he would face mass rebellion from his own party and Vice-President. It is unthinkable he would permit war crimes tribunals of the Party colleagues who ordered this torture.

The advocates of torture love to wheel out the ticking bomb scenario served up every week on 24. But think about what it requires. You have to (a) be certain you have captured a bomber in the very brief window between him planting a bomb and it blowing up, yet (b) have no idea where the bomb is. This has never happened, anywhere in the world, ever.

No: what happens in reality is Yehiya Hamoodi. You get a man you kinda-sorta suspect; you torture him; and you get junk intelligence leading you up wrong paths. What would you confess to if I put a gun to your head and started counting down from five?

Once you start to torture it doesn't just stay in the neat mind-experiments favoured by philosophers. After the Israeli supreme court approved torture in very limited circumstances, soldiers were soon torturing two thirds of the Palestinians they held captive. Professor David Luban explains: "Escalation is the rule, not the aberration. Abu Ghraib is the fully predictable image of what a torture culture looks like."

There are no recorded instances of getting useable intelligence from torture – but even if in some freak instance after you have tortured a thousand Yahiyas you finally did, would it outweigh the damage of handing al Qaeda a thousand new recruits, vindicating Bin Laden's hate-talk and breaching the most basic moral codes?

The gap between the Republican and Democratic Parties is too narrow, but on this issue it is hefty. The Republicans have curdled into the Party of Torture, bullying their torture-victim nominee into backing their barbarism, and proudly picking a torturer as their candidate for Congress. That sound of screaming from inside the Palin-drome isn't just from fawning Republicans – it's from men like Yehiya.

j.hari@independent.co.uk