As he strode up the steps of the courthouse in Greensboro, North Carolina, last week, John Edwards still looked the part. True, there's the odd line on his face now, but who wouldn't have been aged by what has happened to him? The rest, though, was virtually unchanged: the same trim figure; the same head of perfect chestnut hair, sleek as a sable wrap; the same winning smile.

But this wasn't the John Edwards of yesteryear, the ridiculously successful trial lawyer who, when he was elected to the Senate in 1998, was hailed as the next Bill Clinton. This was today's John Edwards, 58 years old and one of the most despised men in America, about to face criminal trial for campaign finance violations that could send him to jail for 30 years.

Just two years after entering the Senate, he made it on to Al Gore's shortlist of potential vice-presidential candidates. If you thought it was all too good to be true, you needed look no further than his wife, Elizabeth, homely, straightforward and honest as the day is long, and you were instantly reassured.

By 2004, Edwards tried for the White House himself, ending up as running mate to John Kerry. In 2008, he was a candidate again. This time his campaign was a brief footnote to the epic battle between Barack Obama and Hillary Clinton.

In the meantime, the real story was unfolding out of sight. It is a lurid and despicable tale of lies and adultery, exposed not by The New York Times but the tabloid The National Enquirer.

Many of the actors have been called to testify. Whether Edwards himself will be among them is unclear; the once dazzling courtroom performer may conclude that such abilities are now a liability. But among the defence witnesses are his and Elizabeth's eldest daughter, Cate, as well as Rielle Hunter, Edwards's mistress and campaign film-maker.

For the prosecution, the key witness is Andrew Young, the Edwards aide who handled the Hunter cover-up, paid for by two secret donors who contributed some $900,000 (£568,000). Such was Young's then loyalty to his boss that, although a married man, he claimed to be the father of the daughter Hunter bore Edwards. Yesterday's courtier is today a bitter man. In 2010, he published a tell-all book, The Politician, recounting the scarcely believable story.

Missing, alas, will be the donors themselves. One is dead, while the other, the banking heiress and socialite Rachel "Bunny" Mellon, is 101 and deemed too frail to make the trip to North Carolina. And absent, too, of course, is Elizabeth Edwards. She died 15 months ago of the cancer whose recurrence her husband announced in March 2007, even as he was carrying on his secret affair.

The legal case hinges on whether Edwards knew about the payments; and whether they were gifts or political donations expressly to cover up a scandal. If they were the former, no problem. But, as political contributions, they were illegal, far in excess of the then permitted maximum donation to a candidate, of $2,300.

Unarguably, Edwards's conduct was despicable. He betrayed his friends, his family and the voters. His hypocrisy and recklessness remain breathtaking. But everyone has forgiven Clinton, Edwards is said to lament to those friends he has left; why haven't they forgiven him? The answer is that Hillary Clinton was not dying of cancer during the Monica Lewinsky affair, and Bill Clinton never made an idyllic marriage a centrepiece of his campaign.

Even so, cheating on one's cancer-stricken wife and lying about it on television are not crimes. Technically, to receive two secret campaign contributions totalling $900,000 is. But if Edwards is found guilty, it will ring extremely hollow in this age of the super PACs (political action committees), which allow wealthy individuals to give millions to candidates.

This prosecution is without precedent; if successful, it would empower the government to go after virtually any form of campaign spending. The case reeks of partisan politics. The North Carolina prosecutor who led the indictment is a diehard Republican who is now running for Congress – with the Edwards affair a centrepiece of his campaign.

You can't escape the feeling that the case is being driven by a determination to kick a man when he's down. And Edwards is nearly out for the count. As a lawyer and a politician, he's finished. He's a single parent bringing up two teenage children, a pariah in his community, reportedly forced to do his shopping at dead of night in 24-hour supermarkets. And he's on his own in a vast house paid for by his successes as a trial lawyer, but haunted by the ghost of Elizabeth.