* Iconoclastic comedian heading for strong showing
* First general election for his grassroots movement
* Raging rhetoric a stark contrast to professorial Monti
By Lisa Jucca and Sara Rossi
MILAN, Feb 19 (Reuters) - The leader of an anti-establishment movement that is set to come third when it contests its first general election in a few days whipped a crowd of more than 30,000 into a rage against Italy's corrupt political system on Tuesday.
Beppe Grillo, a charismatic former comedian known for his foul-mouthed jokes, asked established politicians to "surrender" to the Italian people, drawing applause and cheers from the masses outside Milan's gothic cathedral on one of the final rallies of his 'Tsunami Tour'.
"You (politicians) must leave while there is time," he told supporters of his 5-Star movement, a grassroots collective that was built on Grillo's charisma, Internet campaigning and Italians' disaffection with old-style politics.
"You have consumed the entire country, the lives of thousands of people. You must go home," he shouted to boos and shouts of "Send them packing" and "Thieves! Thieves!"
The atmosphere could not have been more different than at a small rally at the other end of the country, where professorial economist Mario Monti gave a sober speech in a theatre in Sicily's capital Palermo.
The former European commissioner is hoping voters will reward his efforts to pull Italy back from the economic brink when he became a technocrat prime minister after Silvio Berlusconi resigned in late 2011.
Wearing a dark suit, he praised the "maturity of the Italians for understanding and accepting the sacrifices we asked of them to not end up like Greece".
The polite applause was nothing like the cheers back in Milan when Dario Fo, a Nobel prize-winning writer and a well-known anti-establishment figure, took the stage to show his support for Grillo.
"Without funds we became not the third, not the second, but the number one political force in the country!" Grillo said, exaggerating his movement's standing at third behind the centre-left Democratic Party (PD), which scored 30.2 percent in an average of final polls published before a pre-election blackout.
The 5-Star Movement was on 16 percent, Berlusconi's centre-right People of Freedom scored 20.8 while Monti's centrist group polled 13.6.
Grillo himself is not standing for election, but is the figurehead leading a team of politically-untested candidates, like teachers and IT workers, who were chosen in an online primary and will remain in opposition if Grillo sticks to his declared refusal to join a coalition with any other party.
On Sunday, a similar-sized crowd gathered in Milan - a crucial battleground in swing-region Lombardy - to hear Pierluigi Bersani, head of the PD and most likely Italy's next prime minister.
But Grillo's exuberance was more reminiscent of the stage performances of Berlusconi, who was showered with adulation by die-hard supporters in Milan on Monday.
In contrast to Berlusconi's adoring and loyal fans, many of those standing in the cold Milan night had not yet decided whether to cast their vote for the comedian from Genoa.
"I am here because I am curious," said Marina Caffagna, a 28-year-old makeup artist. "I share some of Grillo's values, but I do not know whether I am going to vote for him."