“The region has always been governed by the left, also governed well,” said Claudio Casari, a 64-year-old carpenter who cheered Mr. Salvini as his “captain” outside a marine museum in Cesenatico.

But he said that a general Italian malaise had led young people to leave the country and the region, and that Italy needed a strong leader like Mr. Salvini to restore faith. “He brings hope to Italy,” Mr. Casari said.

Mr. Salvini’s many detractors argued that he used his time in government to draw attention to himself and increase his political support with publicity stunts rather than help get Italy out of its slump.

On Tuesday, Mr. Salvini streamed video of himself buzzing the doorbell of a Tunisian family in a working class section of Bologna and asking the person who answered the intercom if their son dealt drugs, as locals asserted. The Tunisian ambassador protested that the incident “was a deplorable provocation” that “stigmatized the whole Tunisian community in Italy.”

But national leaders of the Democratic Party are loath to make their case on the ground in Emilia-Romagna, and have largely steered clear of the region to keep the race local and play down the consequences if they lose.

Enthusiasm there has largely come from the Sardines, a liberal grass-roots movement created to stop Mr. Salvini.

The Sardines packed Bologna’s main square with tens of thousands of people on Sunday night and plan to close out the race with a rally in the beach club where Mr. Salvini spent most of the summer. They have repeatedly taken credit for infusing the candidacy of the region’s incumbent governor, Stefano Bonaccini, with life.