ROME (AP) — Silvio Berlusconi has survived corruption charges, a sex scandal and a nasty public divorce, but a break with a key ally could spell the beginning of the end of a 16-year political career for the multibillionare businessman.

Two years after he swept to power for a third time, the Italian premier finds his parliamentary majority eroded and now faces a key vote in parliament Wednesday that could signal serious troubles for his government — and eventually lead to a snap election in the fall.

"These are the spasms of the end of a regime," said Stefano Folli, a leading political analyst.

The premier split last week with the charismatic Gianfranco Fini, an ally since Berlusconi's entry into politics and the co-founder of the People of Freedom party. The two had bickered for months on a number of issues, and finally Berlusconi accused Fini of mounting an opposition from within, and effectively expelled him from the party.

Berlusconi insists his government is stable, but many see his hold on power weakening as his personal image withers. La Stampa newspaper said the crisis has tarnished Berlusconi's aura of being "omnipotent, untouchable, magical."

"Silvio Berlusconi himself is reduced to being a politician like all the others," it said.

Indeed, Berlusconi is vulnerable in the lower house of parliament, where a breakaway group of 33 lawmakers loyal to Fini has deprived Berlusconi's party of its majority. In the Senate rebels have reduced Berlusconi's majority to a handful of seats.

The lower house votes on a no-confidence motion against a Cabinet undersecretary entangled in a scandal. Fini's lawmakers are expected to abstain. That would sink the no-confidence vote against Giacomo Caliendo, because such motions need a majority of 'yes' votes to pass.

However, mass abstentions from an erstwhile ally would be a major embarrassment for Berlusconi and show how much clout Fini, who has moved from his neo-Fascist past to the political center, now yields.

The rebel lawmakers insist they will remain loyal to the government if it implements key planks of their joint 2008 electoral platform. But they also say they have free hands when it comes to other issues.

When cornered and weakened, Berlusconi responds by exuding confidence — and threats to demand early elections have been a common ploy.

The decision to dissolve parliament and call new elections rests with the president of the republic, but if Berlusconi consistently fails to muster a workable majority the president might ultimately have little choice but to call an early ballot. The government's term ends in 2013.

Berlusconi can count on the fact that the main opposition party still lacks clear strategy and strong leadership, and an early election would leave Fini little time to organize his future moves, and possibly his own political party. Even as Berlusconi's approval ratings have fallen to 41 percent in early July from 50 percent in May according to a recent poll, the premier remains popular among many Italians.

But it would be a dangerous game, even for a man who has weathered criminal trials, international gaffes and his support to war in Iraq despite the opposition of millions of Italians. Fini is admired by many as a skilled politician and scores high in opinion polls, although so far he has failed to attract a voter base capable of challenging Berlusconi's.

The premier turns 74 next month, and has been engulfed in a sex scandal centering on his dalliances with young women and his encounter with a prostitute.

Reports of parties at his mansions with scores of young women, in one case dressed as "little Santas," photographs of topless women lounging at his Sardinian home and alleged wiretaps of his encounter with self-described escort Patrizia D'Addario dominated headlines for months last year.

The premier has denied ever paying for sex, though he has admitted he is "no saint." His wife filed for divorce, saying she was fed up with his infatuation with young women.

The scandal has deprived Berlusconi of his dream of becoming president of the republic, a largely ceremonial post generally held by a widely respected political figure of high moral standards. The president is elected by parliament, not directly by voters.

Adding to Berlusconi's woes, several corruption probes have touched members of his government or officials close to him. The industry minister was the highest-ranking official to resign amid one of these probes, and the post has yet to be permanently filled.

Berlusconi has often defended his aides and attacked what he says are politically-driven prosecutors — stirring tensions with Fini who has adopted a tougher stance toward public servants suspected of corruption. A recent probe alleging that a secret society sought to influence politics and the judiciary has involved a senior official in Berlusconi's party, who denies wrongdoing.

A government collapse might also have legal consequences for Berlusconi.

The premier is a defendant in two ongoing trials, but a measure passed by his conservative forces suspends the proceedings for up to 18 months if the defendant has a "legitimate impediment" stemming from being an elected official. The law was designed as a stopgap measure to buy the conservatives time while they prepare more thorough immunity legislation for top officials.

Berlusconi is a defendant in two trials in Milan, one on corruption charges, one on tax fraud charges. He denies wrongdoing.