This is judgement day on one person above all: the country's Prime Minister, Silvio Berlusconi. Polling continues tomorrow, and not long after the polls close at 3pm it will become clear whether Italy's richest man wins a new mandate or loses everything: the power and prestige of high office, his monopoly control of Italian television and, conceivably, his freedom.
He's not the only one. If Mr Berlusconi, Tony Blair's closest European ally, goes down, then a large metal door could also be clanging behind his erstwhile associate, David Mills, estranged husband of the Culture Secretary, Tessa Jowell. The pair are accused of conspiring to obstruct the course of justice at a trial which has its first hearing next month.
After a month off the agenda, the affair has suddenly bounced back into the headlines with the Italian leader denouncing the prosecutors behind the case in Milan as "shameless and infamous", producing 15 folders of documents. The prosecutors say Mr Berlusconi paid Mr Mills $600,000 (£345,000) to give false testimony in an earlier trial. The Prime Minister claims the documents prove that the money came from a different person altogether: Diego Attanasio, a Neopolitan ship-owner.
Then, by a strange coincidence, in an interview with Legal Business last week, Mr Mills also announced that he had solved the mystery of the $600,000. "By sheer chance, the most extraordinary chance, last night," he said, "I discovered a piece of clinching evidence that the money came from Diego Attanasio."
The main problem with both men's claims is that Mr Attanasio adamantly denies paying the money. And his alibi is good: he was in jail at the time. But Mr Mills is equally adamant that he has found the final, exonerating piece of evidence, and has made available to the Italian media documents purporting to show the financial structure he built for Mr Attanasio. It is these documents that finally "kill the malicious corruption allegations", he has told friends. But the Milanese prosecutors pursuing the case are refusing to admit Mr Mills's documents, and the case is still set for its first committal hearing on 5 June.
By then Mr Berlusconi will either be in power, or deep trouble.
If he wins, he will consolidate his power and move to protect himself permanently from the law. He has vowed to break the magistrates who have been on his tail for more than a decade. Italy's justice system is overloaded, underfunded and beset by a bureaucratic culture, all of which make it hard for the common citizen to get speedy justice.
But it has a prosecuting system that enjoys freedom from political control, and a feisty sense of the importance of its independence. A top priority for Mr Berlusconi, if he gets back, will be to castrate those turbulent prosecutors.
One of the reasons he has done so little to enact meaningful reform in Italy over the past five years is that he has devoted most of his political energy to getting laws passed to protect himself: to allow trials to be transferred to more indulgent judiciaries; to give himself immunity from prosecution, to protect his media empire from assault on the grounds of its being a monopoly, and to forestall "conflict of interest" attacks on his position as media tycoon and Prime Minister.
He has passed these ad personam laws without betraying any sense that he was making indecent use of parliament: for Silvio Berlusconi, l'état, c'est moi.
As his violent rhetoric of recent days makes clear, he is no longer capable of seeing any difference between his own interests and those of the nation. Anyone (like Milan's prosecutors) who is against him is a subversive against Italy. "Berlusconi," wrote one former editor, "seems devoted to the task of making the entire nation part of his clan." He still makes foreigners laugh, but these are some of the reasons why nowadays he makes many Italians gag with fright.
If he loses, however, his choices will be far more limited. He has made it clear he has no intention of going into exile or dropping out of politics. If Forza Italia is once again the predominant party on the centre-right, as is almost certain, he will insist on being leader of the opposition, and will not give the new government a moment's rest.
If the centre-left wins unconvincingly, he will be counting the days until its internal contradictions start to cause it to unravel. Through his media assets he will ferociously harangue the government and attempt to whip up mass protests against any assault on his concentration of media power. He is a master of this. When in 1984, during his early years as a media mogul, judges tried to close down his nationwide television network, which was operating in a legal vacuum, he short-circuited them.
Yanking popular programmes such as Dallas and General Hospital from the screens, he gave the impression that this was the work of the judges, provoking an inundation of angry phone calls. Years later, he galvanised his viewers into mass protests against a government plan to ban "tele-promotions", the advertising of products within quiz or talk show programmes, which earned him millions a year.
Mr Berlusconi has a deep understanding of the value of political power.
When he decided, against the wishes of his advisers, to throw himself into politics in 1993, criminal cases against him were piling up. His empire was dramatically in debt and facing the threat of bankruptcy. A mere two months after telling viewers of his three TV stations, in a long, pseudo-presidential address, of his plan to "scendere in campo", to go down on to the pitch of politics, he was Prime Minister. Suddenly, the machinery - political, judicial and economic - that had threatened to destroy him was in his hands.
Only seven months later, his coalition collapsed after a key ally rebelled against his autocratic style. In the following six years of centre-left rule, Mr Berlusconi could have faced the dismantling of his empire and disgrace in the courts. Luckily for him, his adversaries on the left arrogantly believed that he was finished. So instead, they treated him as a partner, and passed a law that had the effect of spinning out trials - giving him a much better chance of seeing the cases against him killed off by the statute of limitations.
Having what they regarded as bigger fish to fry, the centre-left did not bother to enact a law to bar a monopolistic media tycoon from returning to power. So it was, with his empire intact, that Mr Berlusconi rampaged back to power in the 2001 election, his centre-right coalition gaining a crushing majority.
Massimo D'Alema, the former prime minister blamed for failing to take action to hamstring Mr Berlusconi back in the Nineties, has vowed not to make the same mistake next time. President of the Left Democrats, Mr D'Alema has promised that, if elected, the centre-left under Romano Prodi will pass a law requiring a prime minister to put his commercial interests into a blind trust, as is done in the US. "We don't want revenge," he said, "and we don't want to destroy anything, least of all [Mr Berlusconi's TV company] Mediaset ... But [Mr Berlusconi's mono- poly] is a democratic anomaly that one cannot find in any other country."
It's not in their manifesto, but the centre-left is also determined to abolish Mr Berlusconi's latest legal reform, which halves the time allowed for white-collar criminal cases to negotiate all three levels of the court system before they are annulled by the statute of limitations. If a centre-left government passes these measures, Mr Berlusconi will lose all say in the content of Mediaset's TV channels and his daily papers.
ITALY GOES TO THE POLLS
47m Italians are eligible to vote in this election. More than a million Italians living abroad have already cast their votes
630 seats are at stake in the House of Deputies. Another 315 seats are also up for election today in the Senate of the Republic
The most outlandish claim: "Under the China of Mao they didn't eat babies, they boiled them to fertilise the fields" (Silvio Berlusconi)
Unlikely comparison: Jesus Christ, or Napoleon (Berlusconi, of himself)
Prodi on Berlusconi: "It would be better if he stood on an empty chair. That way he would reach normal height"
Berlusconi on Prodi: "He is no more than a front man [for the Communists]...a useful idiot ... a cuckold ...a rabbit..."