But their efforts to intimidate Mr. Mattarella last week, saying he should not get in the way of Italian voters, failed. Some supporters argued that the potential blowback and risk in coming elections was worth keeping the populists, who have shown disregard for Italian institutions, away from power.
Mario Calabrese, the editor of the left-leaning daily La Repubblica, wrote in a front-page editorial, “If the president had given in, folding before the ultimatums and threats, and if he went back on his only objection, the state’s checks and balances would have broken into pieces.”
Mr. Berlusconi, the former prime minister and coalition partner of Mr. Salvini, also gave his support to Mr. Mattarella, saying the Five Star Movement was “irresponsible as always, talking about impeachment.”
“Forza Italia waits for the determination of the head of state, but when necessary will be ready for the vote,” he added, referring to his party.
That supportive language caused signs of a fracture with Mr. Salvini, who said Mr. Berlusconi’s defense of Mr. Mattarella made him sound like Chancellor Angela Merkel of Germany. Mr. Salvini hinted that he was also open to running with the Five Star Movement in the coming election, saying that the policy agenda the two parties had hammered out was not “scrap paper,” and that there was “a good base for working together.”
Both he and the Five Star Movement unveiled campaign language in which they accused Italy of being held hostage by Germany, international markets, bankers and the overreaching president who did their bidding.