“It’s too simplistic to say it works in the government’s favor,” Mario Calabresi, the editor of the Turin newspaper La Stampa. “But today, instead of talking about the problems of the country, everyone is talking about the violence.”

The center-right government sought to blame left-wing groups and their sympathizers. Defense Minister Ignazio La Russa attributed the violence to a tone used by the Italian left in which “everything is justifiable as long as we can get rid of Berlusconi.”

Those arrested, however, did little to lend credence to that accusation. News reports said that some of the 12 arrested were believed to belong to right-wing soccer fan groups, while others were linked to self-styled anarchist groups.

To some Italians, the images of Rome in flames cast light on the government’s shortcomings, suggesting that a government elected promising law and order and led by a salesman once perfectly attuned to the national mood had lost control not only of the demonstration, but also of the economy, and increasingly of public opinion.

The violence came at a time of deep political uncertainty.

“Italians are indulgent toward the government because they don’t see that there’s an alternative,” said Massimo Franco, a political commentator for the daily newspaper Corriere della Sera. “But when they realize that the government cannot do anything — and even makes fun of them, especially about the economy — at that point the lack of alternatives isn’t enough.”