He pledged to continue his role as a political leader, citing other figures not in Parliament, namely the founder of the Five Star Movement, Beppe Grillo, and Matteo Renzi of the Democratic Party, tipped by many as a future premier candidate.
"Also, from outside the Parliament, we can continue to fight for our liberty," he said.
Supporters were treated to a video montage of Berlusconi's greatest political hits from a career that began in 1994 when he first came into power with a political party named for a soccer chant "Go Italy". He said that even if he's no longer a senator, he will continue to be a force to reckon with.
"For us he will always be there," said Marilda Antonello as she held a banner reading "The law is not equal for everyone. Sick justice."
"He is our only leader. He is the only man who can take Italy forward," she said.
The Senate vote on whether to remove Berlusconi from the chamber stems from a 2012 law that bans anyone sentenced to more than two years in prison from holding or running for public office for six years. His lawyers claim the law is unconstitutional and have questioned why the rush to expel him while legal challenges are still pending.
Italy's high court on August 1 upheld Berlusconi's tax fraud conviction and four-year prison term stemming from his Mediaset empire's purchase of television rights to US films.
The prison term was reduced automatically to one year under a general amnesty; he will serve his time either under house arrest or through public service.
Berlusconi claims he didn't receive a fair trial and that the judges were biased and out to "eliminate" him from public office. His lawyers have also charged that the 2012 law is unconstitutional and can't be applied retroactively to crimes allegedly committed before it was passed.
They have taken their challenge to the European Court of Human Rights - even though it turns out Berlusconi didn't make much of his Senate role to begin with: Private TV La7 reported this week that Berlusconi attended just one Senate session since April's elections. And that was when he did an about-face and backed the government in a confidence vote after threatening to bring it down.
Nevertheless, Berlusconi made a last-ditch bid to save his seat this week, sending a letter to opposition senators warning them that kicking a three-time premier out of public office would tarnish Italy's image abroad and weigh on their consciences, "a responsibility that in the future will shame you in front of your children, your electors and all Italians".
Berlusconi remains head of his relaunched Forza Italia party, which on Tuesday officially withdrew its support of the government of Premier Enrico Letta and is now in the opposition.
Despite the switch, Letta's government comfortably survived a confidence vote early Wednesday and passed the annual budget. He survived because Berlusconi's one-time political heir, Angelino Alfano, split from his mentor earlier this month and formed his own new centre-right party that remains loyal to Letta.
Analysts said they expected Letta's government - a hybrid of his Democratic Party and Alfano's New Center-Right - would continue in the short term.
The opposition, however, now includes two strong leaders: Berlusconi and Grillo, whose populist Five Star Movement encapsulates the discontent many Italians feel with the country's byzantine politics.
"Berlusconi by himself doesn't have the strength to bring down Letta's government, but he's going to make it more difficult for the Democratic Party to stay in the majority," said Giovanni Orsina, deputy director of the school of government at Rome's LUISS University. "I think Silvio Berlusconi can do some damage to this government."
James Walston, a professor of international relations at the American University of Rome, said the vote and rally essentially mark the start to a new electoral campaign in which Berlusconi won't be running for office but will be very much a protagonist as the head of a party.
"Berlusconi over the last few days has been conducting a very strident campaign," Walston said, referring to his letter to the opposition senators. "This is Berlusconi laying down part of his program for what he hopes is going to be elections very shortly."
Meanwhile, Berlusconi still faces other legal problems, including a seven-year prison term and lifetime ban from holding public office for his conviction of paying an underage prostitute for sex at his infamous "bunga bunga" parties and trying to cover it up. He has professed his innocence and plans to appeal.
- AP
