ROME — For years, former Prime Minister Silvio Berlusconi deftly navigated the labyrinth of Italian justice, always finding an exit — until Thursday, when Italy’s highest court handed him his first definitive sentence, upholding a prison term for tax fraud and sending Italy’s fragile government on the road to crisis.

The court called for a re-examination of a ban on Mr. Berlusconi’s holding public office, but did not reject the ban. This staved off the imminent collapse of the right-left coalition of Prime Minister Enrico Letta, which was formed to tackle Italy’s dire economy — but probably only bought it more time.

Parts of Mr. Letta’s center-left Democratic Party are reluctant to share power with a now-convicted criminal. Meanwhile, the center-right People of Liberty party looked poised to split between Berlusconi loyalists and those seeking more independence from the former prime minister in a future bloc.

“The barometer signals a very strong storm,” said Giovanni Orsina, professor of contemporary history at LUISS Guido Carli and author of “Understanding Berlusconi.” “I expect a lot of quake tremors in the next few days, but I think that the government will survive.”