ROME — A special panel of the Italian Senate on Friday voted to strip Silvio Berlusconi of his current seat, a humiliating blow for a man who has dominated Italy for the past two decades but whose political career is now very much in jeopardy.

The expulsion vote against Mr. Berlusconi, based on his recent tax fraud conviction, was his second setback of the week, after his failed attempt to bring down the country’s fragile coalition government. The full Senate will probably decide by the end of the month whether to expel Mr. Berlusconi, though a vote against him is now considered very likely.

Mr. Berlusconi, 77, a former prime minister and billionaire media mogul, who once wielded power with a swagger, had fought for weeks to prevent the expulsion vote. Many analysts say his effort to topple the government was partly intended to interrupt or delay the proceedings against him in the Senate. But a mutiny of his center-right supporters forced him to make a public reversal and support the government in a parliamentary confidence vote.

“It’s a loss on all fronts for a man who is at the end of his career,” said Stefano Folli, a political commentator for the daily newspaper Il Sole 24 Ore. “Now his twilight will be swifter. This clearly has a highly political and symbolic value.”