Last week the American anti-war left had a ball. The bereaved mother of a soldier killed in Iraq, Cindy Sheehan, decided to camp out near President Bush’s holiday ranch in Crawford, Texas, to protest against the war.

MoveOn, the far-left group behind much anti-war activism, organised solidarity gatherings across America. Viggo Mortensen, the Lord of the Rings star, turned up. The left-blogs gushed. A bored media, left with only the historic withdrawal from Gaza and a new Iraqi constitution, finally saw a way to cheer themselves up in the Texas desert.

The only catch in this win-win spectacle for the press and the peaceniks was Sheehan herself. Her views on America’s role in the world are to the left of George Galloway. “The biggest terrorist in the world is George W Bush,” Sheehan said in a recent speech. “What they’re saying, too, is like, it’s okay for Israel to have nuclear weapons. But Iran or Syria better not get nuclear weapons . . . It’s okay for Israel to occupy Palestine . . . for the United States to occupy Iraq, but it’s not okay for Syria to be in Lebanon. They’re a bunch of (expletive) hypocrites.”

Sheehan went after Bush’s kids: “If (Bush) thinks that it’s so important for Iraq to have a US-imposed sense of freedom and democracy, then he needs to sign up his two little party-animal girls. They need to go to this war . . . We want our country back and, if we have to impeach everybody from George Bush down to the person who picks up dogshit in Washington, we will impeach all those people.”

Oh dear. She has every right to speak her mind; and every right to grieve for her son; and every right to oppose the war. But she is an extremist. Someone who wants to impeach litter cops in Washington for a war that deposed one of the grisliest dictators of modern times is not someone to take seriously.

There is no pleasing her. As the mother of a fallen soldier, Sheehan demanded an audience with the president. She got one. She demanded another. She was sent Stephen Hadley, one of Bush’s closest foreign policy advisers instead. Not enough.

The Sheehan left wants swift withdrawal from Iraq, whatever the consequences. It wants Democrats back in power. It can’t wait for another election; and it still believes that something was rigged about the last one. When you read the anti-war blogs or a New York Times columnist, you get the sense it actually wants Iraq to fall apart, or Al-Qaeda to regroup, or another terrorist atrocity to succeed. Hurting Bush is the overwhelming, empowering imperative.

If you want to know why the opposition is still weak even while the Bush administration remains riddled with error and denial, Sheehan is a good place to start. The emotional blackmail, the extreme rhetoric, the lack of any practical alternative to the current course in Iraq: these do not a future administration make.

But there is another opposition — more grown-up, less volatile and therefore more effective. You can see it in the very measured way in which Senator Hillary Clinton has visited US troops in Iraq, and argued for higher troop levels and more careful diplomacy.

You are also seeing it among Republican leaders who want to win the war but know that the cramped cocoon of Donald Rumsfeld and Richard Cheney is unlikely to get us there. Senator John McCain went fullout for Bush’s re-election but has repeatedly said that he has no confidence in Rumsfeld’s war management.

Senator Chuck Hagel of Nebraska, a ferocious critic of the mishandled post-war era, recently toured his bedrock Republican home state and found real worries. “The feeling that I get back here, looking in the eyes of real people, where I knew where they were two years ago or a year ago — they’ve changed,” Hagel said last week. “These aren’t people who ebb and flow on issues. These are rock-solid, conservative Republicans who love their country, support the troops and the president . . . The expectations that the president and his administration presented to the American people two and a half years ago is not what the reality is today. That’s the biggest credibility gap problem he’s got.”

It was the determination of adult Republicans and a handful of similarly grown-up Democrats who averted the abolition of the Senate filibuster earlier this year. They also helped encourage the White House to nominate John Roberts, a sane, careful jurist, to the Supreme Court rather than an ideological knuckle-dragger. They have begun to exercise real influence over Iraq policy as well. They know Bush has another three years and that mindless protest will not save Iraq or win the broader war. They want to help: putting more troops if necessary into Iraq, monitoring more closely the training of Iraqi security forces, correcting some of the more glaring errors of judgment in Bush’s inner circle.

Take prisoner policy. It takes real partisan blindness not to acknowledge that the Bush administration’s decision to exempt terror detainees from the Geneva Conventions, to relax legal strictures on abuse, and to set up extra-legal camps such as Guantanamo Bay have led to moral horrors and massive propaganda own goals.

So Republican senators McCain and Lindsey Graham are trying to provide new legislative guidelines for prisoners of war to bring policies back into line with historic American concern for humane treatment of even the most abhorrent captives. They hope to attach such regulations to the military appropriations bill to be debated this September. They may even exempt the CIA in a bow to White House sensibilities.

Cheney and Rumsfeld are mounting a ferocious counter-offensive, to kill any regulation of the president’s post-9/11 ad hoc powers to permit torture or abuse. Partly it’s the belief that the president should be above the law in wartime; partly it’s a defence of their own complicity in the policies that led to the abuse; partly it’s simple turf war.

The battle is real: the war has to be funded; and if McCain and Graham succeed in getting a majority of senators to back their proposals, it will be managed by more than a cabal of proven incompetents.

The real opposition has been elected to the Senate. We will find out this autumn how effective it is.