Silvio Berlusconi during a voting session at the Senate in Rome last month.
ROME — Italy’s highest court was expected to rule on Thursday afternoon on a closely watched tax fraud case that could end the political career of Silvio Berlusconi, the country’s most dramatic figure, and significantly weaken its right-left coalition government, with repercussions throughout the euro zone.
If the Court of Cassation upholds his conviction, Mr. Berlusconi will face one year in prison and be banned from holding public office for five years. That outcome would upend his center-right People of Liberty party, more a charismatic movement than an ideologically coherent party, and also strain the center-left Democratic Party, elements of which have never liked sharing power with their former rival.
Most analysts predicted that some form of compromise for the government could be reached, however much it strained the limits of Italian democracy, and that the government of Prime Minister Enrico Letta would not fall. Still, the possibility has pushed the country, struggling to stay afloat amid a deep recession, into ever-stranger political waters.
In opening arguments on Tuesday, the public prosecutor said that Mr. Berlusconi was “the mind” behind the tax fraud and the prosecutor asked that the court uphold a one-year prison sentence. But he asked for a reduction in the ban on public office to three years from five.
Mr. Berlusconi’s defense lawyer called this a “blatant error” in sentencing.
The ruling would be the first definitive sentence for Mr. Berlusconi in 20 years of tangles with the judiciary. In the other cases — which range from tax evasion to buying judges to embezzlement — he was either acquitted on appeal or the statute of limitations ran out.
In a separate case, Mr. Berlusconi also faces trial for paying for sex with the Moroccan-born Karima el Mahroug, nicknamed Ruby Heartstealer, when she was still a minor, and abusing his office to cover it up.
Experts said that if the high court upheld the tax fraud sentence, Mr. Berlusconi would more likely face house arrest, considering his age, 76. His earlier sentence of four years was reduced to one under a law aimed at combating prison overcrowding.
If there is a final ruling, the Senate will still have to rule on whether Mr. Berlusconi must resign from public office, a procedure that could take months. Almost all lawmakers handed definitive sentences have chosen to leave Parliament of their own volition in order to avoid embarrassment.
But that is not Mr. Berlusconi’s style. In comments published on his party’s Facebook page, Mr. Berlusconi, a former prime minister, said he was prepared to go to prison if he was convicted, and would not go into exile like Bettino Craxi, Italy’s former Socialist leader, who died in exile in Tunisia after a party-finance scandal that brought down the Italian postwar political order in the early 1990s.
The imminent ruling has once again brought Mr. Berlusconi to the fore of the national conversation, where he occupies far more space and airtime than Mr. Letta, the current prime minister.
Still, on Thursday in Italy’s leading economic newspaper, Il Sole 24 Ore, the political columnist Stefano Folli wrote that he expected the court to find a “compromise” ruling that would not ban Mr. Berlusconi from Parliament, guaranteeing more political stability.
He added that after weeks in which waiting for the ruling had “substantially suspended public life” in Italy, a compromise could be even more destabilizing, because it would take the pressure off the right-left coalition, which grew out of a political stalemate with a mandate to confront Italy’s economic emergency and has produced few results.
“The partial rescue of the most burdensome character in Italy’s political life cannot have as a consequence the postponement of the country’s problems,” Mr. Folli wrote.
For days, Mr. Berlusconi’s core of loyal supporters has been up in arms, lambasting the Italian judiciary for what it sees as its attacks on him, and some members of Parliament from his People of Liberty party have hinted that they would leave the government if he was convicted.
Others seem to be enjoying the spectacle. A verdict that was upheld would be “the death of democracy,” Daniela Santanchè, a former government official best known for her frequent television appearances defending Mr. Berlusconi, wrote on her Twitter feed.
Many, even on his own legal team, said they believed the court would uphold the sentence in some form.
The Court of Cassation could overturn the sentence and free Mr. Berlusconi of all the charges, or ask for the case, or parts of it, to be re-examined by a different appeals court. Pending a final ruling, Mr. Berlusconi could still hold office.
Milan prosecutors argued that Mr. Berlusconi and other defendants bought the rights to broadcast American movies on his networks through a series of offshore companies and falsely declared how much they paid in order to avoid taxes.
The dozens of trials involving Mr. Berlusconi have often caused political turmoil. In July, members of Mr. Berlusconi’s party stormed out of Parliament and blocked parliamentary activities for a day after the court set the hearing for the tax fraud case earlier than expected.
Gaia Pianigiani contributed reporting.
