Even before he'd started to speak, the signs were of a performance that lacked his usual panache. To begin with, the microphone that Silvio Berlusconi picked up to address the senate didn't work properly. Once it did, his speech was uncharacteristically flat. There were no histrionics or garrulous jokes – just a final sentence which, in a few rather sheepish words, spoke volumes.

The man who had dominated Italian politics for two decades had been forced into a humiliating climbdown by a rebel faction of his own MPs. Outfoxed, out of luck and abandoned as never before, he looked tired and downcast. But he brought a smile and incredulous chuckle to the face of Enrico Letta, the prime minister.

"Italy needs a government that can carry out structural and institutional reforms which the country needs to modernise," said Berlusconi, his hands clasped in front of him, an Italian flag pin on his lapel. "We have decided, not without internal strife, to vote in confidence."

There was a burst of applause. But Il Cavaliere, as the Italian media like to call the billionaire former prime minister and convicted tax fraudster, had nothing to cheer about.

In a fittingly dramatic denouement to a political saga that a former minister likened to a tragicomedy and an MP said was more like a farce, Italy's government crisis – a week of mounting dread and trembling markets that had risked scuppering the grand coalition and plunging the eurozone heavyweight into turmoil – was over, just like that.

Letta, the centre-left leader of a government which since its inception has been plagued with tensions and ideological splits, went on to win the senate confidence vote with a sweeping majority. Only 70 of 305 MPs voted against; 235 MPs voted for. Berlusconi – the man who triggered the crisis and spent days clamouring for the government's downfall – was one of them.

Later, in the lower house of parliament, a vindicated Letta said it was time to call a halt to the threats and ultimatums which had dominated the coalition since Berlusconi's first definitive criminal conviction on 1 August.

"Italy needs there to be no more blackmail of the 'do this or the government falls' sort," he said. "Italy doesn't need any old government, but a government at the height of its abilities with a clear majority supporting it."

The prospect of more stability was music to the markets' ears. The FTSE MIB was the best-performing stock market index in Europe, up 0.7%, while Italian debt strengthened in value, pushing down borrowing costs and sending the yield on Italy's 10-year bonds to 4.37% from as high as 4.74% on Monday morning. They were not the only ones to be relieved. Ever since ominous drumbeats started sounding last week, concern had grown not only among Berlusconi's opponents but large parts of Italian society about what lengths he was prepared to go to in order to – in Letta's words – "protect his personal interests".

Facing imminent expulsion from the senate and the enforcement of his commuted one-year sentence, the recently convicted People of Freedom (PdL) party chief had insisted that his motive for suddenly withdrawing his ministers from the government was a sales tax hike imposed by the coalition that he had vehemently opposed.

Even by Berlusconi's standards, however, this was hard for Italians to swallow – even, it transpired, for most of the very ministers he had ordered to resign. One by one, four of them lined up to voice their misgivings. Their exact status was unclear; La Repubblica, translating the uncertainty into punctuation, referred to one of them as an "ex(?) minister". By Tuesday night, however, in the latest step in an increasingly bizarre political dance, Letta made an announcement to the effect that the five could resign all they liked; he was not accepting their resignations.

In the senate on Wednesday, the stage was set not only for a showdown between Berlusconi and - as Il Sole 24 Ore wrote – "the whole world – Europe, the United States, the markets, the [semi-official Vatican newspaper] Osservatore Romano". It would also be a vital test of whether the leader of what has always been a personal party built around Berlusconi the man - his success, his power and his bravado - still called the shots.

As it turned out, he did not – not, at least, in the way he once would have done. With his family newspaper condemning the flabbergasting "patricide" of Angelino Alfano, the PdL secretary widely seen as Berlusconi's heir who emerged as leader of the rebels, the 77-year-old arrived at the senate around 25 minutes into Letta's make-or-break speech

"Italy is running a risk that is potentially fatal, without remedy," the prime minister told MPs, warning them of the damage to the country's economy and image that a government collapse and eventual fresh elections would inflict. "Thwarting this risk, to seize or not seize the moment, depends on the choices we will make in this chamber. It depends on a 'yes' or 'no'."As he sat in Palazzo Madama, his expression grim, Berlusconi, the longest-ruling prime minister Italy has known since the second world war, was greeted by a succession of supporters, many of them among the so-called PdL "hawks". One of them, a former MP named Daniela Santanchè, a loyalist so fierce she is known as "the pythoness", was reported to have offered on Sunday to give Alfano her "head on a platter" if it helped her boss.

But as the day wore on it became clear that a significant portion of Berlusconi's party was going to defy his wishes and vote for the government to continue. Arithmetic on a scribbled piece of paper that Alfano displayed had 32 senators voting with their leader, 24 absenting themselves, and 25 against him. With such numbers, Letta was home and dry. And Berlusconi, not long after the party line was voted and confirmed to be for the "sfudicia", then got up in parliament and performed a screeching U-turn.

The prime minister, perhaps, could be forgiven a small smile. Later, the editor of La Stampa, tweeted him reminding him that, on Sunday, Letta had likened Italian politics to Groundhog Day, the film in which every day turns out the same. After all that, Mario Calabresi seemed to suggest, Italy had ended up with exactly the same government, with the same problems, as before.

But, said Vincenzo Scarpetta, an analyst at Open Europe, it would be a mistake to think that Wednesday's vote changed nothing. On the one hand, the set-up that Letta has been left with is still far from ideal and "there are still doubts about this government's ability to push forward with painful, unpopular measures," he said. Many suggested Letta would have preferred to have kept Berlusconi out of the majority altogether, thus giving himself a more unified government.

On the other, Scarpetta said, Berlusconi's ability to pull strings and dictate events had definitely been compromised. "He clearly comes out weaker from this. The initial situation when they formed the government was that he would be able to pull the plug on it whenever he wanted, because the government depended on his support. But now, that's exactly what he tried to do … and it didn't work," he said. Analysts said that what happens to the centre-right now will be key in determining whether this is the beginning of the end for Berlusconi, or just a major setback. On Wednesday night, in the lower house, a group of 26 PdL deputies had reportedly signed up to a new centre-right group led by Alfano. Berlusconi loyalists were expected to stay with him under the relaunched Forza Italia party name. "Of course, he remains the leader of the party," said Scarpetta. "We will just have to see what happens to the party."