Liberals called it "Fitzmas". And it was a long time coming. But even though it took almost two years for special prosecutor Patrick Fitzgerald to make it down the chimney, it was worth the wait. Lewis "Scooter" Libby, the chief of staff of vice-president Dick Cheney, faces up to 30 years in prison and a fine of $1.25m if found guilty of lying over his role in leaking the identity of a covert CIA agent. Meanwhile, the continuing investigation of George Bush's consiglieri, Karl Rove, holds out the possibility of further charges against a more senior White House staff member.

In a week that saw Bush withdraw his supreme court nominee, Harriet Miers, and that followed a week in which Tom DeLay, the Republican house leader, was arrested for money laundering and conspiracy, liberals were gorging themselves on a festival of alleged corruption, criminality and incompetence prepared and served by conservatives.

The extent to which these most recent developments have exposed the Bush administration's real agenda and modus operandi should be welcomed. But legal defeats for the right should not be mistaken as political victories for the liberal-left, which has yet to convince anyone that it represents a meaningful alternative.

There is a thin line between what we know to be true and what we can show to be undeniable. Whether it's Rodney King or Abu Ghraib, only with incontrovertible evidence does an assertion shift from a debating point to a reference point. All that separates the misfortunes of Kate Moss from the fortunes of David Cameron is the money shot. We can tolerate the notion that a potential Conservative party leader has taken cocaine so long as we haven't seen it; we cannot tolerate the fact that a waifish model has taken cocaine because we have.

Fitzgerald's investigation crossed that line, laying out in clear detail the proof for some of the central criticisms the liberal-left has asserted about the Bush administration over the past five years.

First, that the case for the invasion of Iraq was built on a lie. This goes to the heart of the matter. Valerie Plame was a covert CIA agent whose husband, the former ambassador Joseph Wilson, was sent on a CIA-sponsored trip to investigate whether Iraq was seeking to buy uranium from Niger for nuclear weapons. Wilson concluded that this was unlikely but the claim ended up in Bush's state of the union address anyhow. When it came to Saddam's supposed weapon's cache, the White House was not the victim of flawed intelligence. It was the wilful perpetrator of known falsehood.

Second, that lie could only be sustained by discrediting those who dared to expose it. On July 6 2003, Wilson accused the Bush administration of exaggerating the case for war in an article in the New York Times. Libby sought to trash Wilson's credibility by telling reporters that Plame helped arrange her husband's trip, thus revealing her identity and sparking the investigation. It is a crime knowingly to divulge the identity of an undercover CIA operative.

For the team that stood a candidate whose wealthy connections ensured he never saw combat while rubbishing the actual war record of his opponent, John Kerry, this was business as usual. Two days after Wilson's piece appeared a Pew poll showed that over the previous four months the number of Americans who believed the military effort in Iraq was going very well had slumped form 61% to 23%; the number of those who thought it was not going well had rocketed from 4% to 21%.

Three months after Bush landed on the USS Lincoln emblazoned with its Mission Accomplished banner, both the message and the mission was tanking; it was time to shoot the messengers along with the Iraqis.

Third, the case has revealed the supine character of America's mainstream media in the run-up to the war. Primarily, it showcased the sharp practices of New York Times reporter Judith Miller. In Miller's own account of her grand jury testimony, she wrote: "When the subject turned to Mr Wilson, Mr Libby requested that he be identified only as a 'former Hill staffer' [rather than "senior administration official"]. I agreed to the new ground rules because I knew that Mr Libby had once worked on Capitol Hill." I once played centre forward for Cygnet Rovers of Stevenage. But to cite me as "a former footballer" would, in most instances, be as true as it is misleading. Miller's uncritical approach amounted to dictation that bolstered the administration's flimsy case for going to war.

"WMD - I got it totally wrong," she told Times reporters recently. "If your sources are wrong, you are wrong. I did the best job that I could."

Neither the Times in particular nor US journalism in general should be judged by the standards of one reporter. But while Miller's reporting style in the run-up to the war was appaling, its content was not aberrant. Following the terrorist attacks of September 11, the administration circled the wagons around the flag and the media found itself on the wrong side. Politically embedded at home before they were military embedded abroad, their fear of appearing unpatriotic trumped their fear of misinforming the public.

So the investigation has given us one of the clearest indications to date of how we got to this point. Given the malevolent partisanship of the Republican party it is not surprising that many liberals gloat at the prospect of a full-scale Republican implosion. But such schadenfreude is premature. The wounds of recent weeks have all been self-inflicted - the result of a mixture of hubris, malice, greed and ineptitude. There is no doubt that they have damaged Bush politically. A Washington Post-ABC poll this weekend shows his approval rating at an all-time low, with the public believing Bill Clinton ran a more ethical administration after the Monica Lewinsky scandal than Bush does now. Meanwhile, An AP-Ipsos poll released on Saturday shows support for the war at an all-time low of 37%.

But the Democrats are not faring much better, with only marginally more support than Republicans, according to a poll taken before the indictments and Miers withdrawal, but after hurricane Katrina and DeLay's arrest.

Having supported the war and without coherent proposals for disengaging, they are ill-placed to take advantage of the Republican's current troubles.

Either unable or unwilling to present a clear agenda of how they would do things differently, they have been effectively mute for several months. With no opposition, popular disenchantment with the Bush Administration's ethical failings is descending into cynicism.

Indeed, the only group that has really flexed its muscles in recent weeks has been the Christian right, which derailed Mier's nomination to the supreme court. Bush is likely to nominate another candidate later this week who will be more to their liking, thereby tipping the balance of the court against abortion and affirmative action. Unless the Democrats develop the wherewithal to challenge them, conservatives will then shape both the law and the politics of the country for a generation. And Fitzmas will be little more than a lingering reminder of what the law can do when politics has failed.

g.younge@theguardian.com