Silvio Berlusconi – never one for sticking to the script – seems bent on inverting the process that Karl Marx identified: that everything in history occurs twice, "the first time as tragedy; the second as farce". For more than 20 years, but particularly in the past five, we have been treated to an increasingly surreal farce. Now, it would seem, we are going to have to watch the tragedy.

As the Italian senate was deciding to expel Berlusconi following his conviction for tax fraud, the man himself was addressing a rally of his supporters outside his home in Rome. There were all the trappings of his heyday: the green, white and red flags of his Forza Italia! ("Come on, Italy!") movement; the playing of the national anthem and of Forza Italia!'s rousing campaign song; the identification in his speech of his own interests with those of the nation; his insistent portrayal of himself, not as a leader let alone a billionaire, but as victim; and finally the bagno di folla, the crowd immersion, with supporters reaching out to the great man, eager to shake, or preferably kiss, his hand.

Yet by the standards of his heyday the crowd was a distinctly modest one. The narrowness of the street that runs in front of his Roman palazzo forced most of the TV teams to record it all with a foreshortened perspective that gave the impression of a forest of banners and placards. But there were really only 2,000-3,000 people (certainly not the 20,000 claimed by Berlusconi's aides). And according to one report they included four busloads sent up from Latina, south of the capital, courtesy of a local politician who is a victim of the same anti-corruption legislation that forced Berlusconi out of parliament.

Italy's most successful politician since the second world war, and its longest-serving modern prime minister, no longer radiates the dazzling aura that blinded his compatriots to his shortcomings and persuaded them to elect him as their leader no less than three times. As Italians struggle to emerge from their longest economic recession since 1945, bitterly reproachful of the stagnation over which he presided in the years that preceded it, Berlusconi strikes an increasingly irrelevant and absurd figure, even to those who once voted for him.

So is he finished? In one sense, he is.

His grip on the destiny of his country has been broken, and there is little chance he will regain it. But the decisive event in this respect occurred, not on Wednesday, but almost two months ago when a section of his party refused to join him in bringing down the coalition government of Enrico Letta (which Berlusconi holds responsible for failing to block his conviction, or at least save him from the consequences).

As a result, Letta's left-right coalition now has a stable majority that includes about 60 of Berlusconi's former supporters. On the day before his expulsion, the former prime minister led what remained of his party onto the opposition benches.

From there, he can huff and puff. But until the ever-shifting pattern of Italian politics undergoes another radical change, he will be unable to bring down the government and force the new elections he would like. Letta has said his goal is to stay in office until 2015. He might even get there – much will depend on the support (or otherwise) of his colleagues in the centre-left Democratic party.

Berlusconi meanwhile will be ageing ever more visibly. Next year, he will be 78. And the effects of his plastic surgery are not improving with time. He is already a convicted felon and from now on he will live in fear of possible arrest.

This week's decision means he no longer has parliamentary immunity: he could be thrown in jail in relation to any of the four trials and investigations in which he is still either a defendant or a suspect. But that is also a reason why, in another sense, the Silvio Berlusconi saga has a way to run.

With all of his trials and legal tribulations, he is certainly not going to disappear from the news. He remains the leader of a party that can count on the support of 129 of the 951 members of the Italian parliament. And he heads a business empire that includes vastly more than just his three television channels.

The party may be over. But like the sort of guest who is the nightmare of every host, Silvio Berlusconi still looks ready to linger for a while on the doorstep.