MODENA, Italy — Antonio Imperato was tending bar one night when he realized that the far right's campaign to reclaim power was heading straight in his direction: anti-immigrant, populist, polarizing Matteo Salvini had announced he was holding one of his next events at Imperato's pub.

“Did you see this?” a regular customer asked the pub owner, holding up his phone and showing Salvini’s schedule, posted online.

Imperato had not — though already a movement to boycott his establishment had begun. He worried about what might come next.

“Should Beyoncé pass by and come in, that is one thing,” Imperato would say later. “But chaos like this is another.”

He had to decide: Should he let Salvini through the door? “I knew that whatever choice I would make would not work,” he said.

Many Italians are struggling with a version of the same question. Salvini was Italy’s deputy prime minister and its de facto most powerful politician until August, when he gambled for even more power and ended up seeing himself sidelined by a new governing coalition. Now a member of the opposition, but still leader of Italy’s most popular party, the League, he is positioning himself for a comeback.

If the League prevails Sunday in a regional election here, in the liberal heartland of Emilia-Romagna, as polls suggest could happen, the humiliation of the left could set in motion a breakup of the government’s fragile left-leaning coalition. That would open the way for new national elections — and give Salvini a chance to become the country’s first far-right leader since World War II.

Already this week, Luigi Di Maio announced his resignation as leader of the Five Star Movement, signaling profound troubles for the governing coalition’s main political force.

Salvini has tried to sell himself as the face of the race in Emilia-Romagna, growing far more visible on the trail than the League’s candidate here, Lucia Borgonzoni.

He keeps a breakneck public schedule and live-streams much of his life, whether buying underwear, musing about the beauty of the moon, eating Italian cheese, getting heckled by senior citizens, spotlighting cases of immigrant crime or going to a newsstand, where the main headlines are often about him.

“It’s a way to show his closeness with the common man,” Imperato assessed.

By the time Salvini arrived on a foggy, chilly night here in Modena, he had already held events that day at a pastry shop, a landfill, a market, an agriculture agency, a restaurant and a cheese producer. Salvini strode through the cobblestone streets, flanked by helpers and cameras, and headed toward a small stage erected on the street just outside Imperato’s pub.

“There’s an energy in Modena that is incredible,” Salvini said just before stepping onstage, but evidence of the political battle lines was there, too.

From a second-floor apartment overlooking the street where Salvini was speaking, a family opened their windows and draped a bedsheet with hand-painted sardines, a symbol of Italy’s new grass-roots opposition to the far right. They then positioned two small speakers near the window ledges and started playing a left-wing anthem, “Bella Ciao,” on repeat.

Claudio Leonardi, 51, the father in the family that had made the sign, said he worries about how Salvini tries to “sensationalize” the danger posed by immigrants, and how social media is “spreading ignorance,” and, above all, how the far right might be a “majority” in the country — though when he looked out the window, he was relieved. He saw only 40 or 50 people, he said, listening to the speech.

Whatever the number — League supporters said the crowd was in the hundreds — Salvini was trying to win their loyalty. He finished speaking and posed for selfie after selfie, sometimes grabbing the phones and taking the photos himself.

“By now,” said Luca Bagnoli, a local secretary for the League, “he knows how to operate every kind of mobile device.”

Then, Salvini finished and was ready for a beer.

Imperato, who has owned the Mr. Brown pub for 15 years, had given conflicting signals about what he’d do. Initially, he’d been caught off-guard about the plans to hold the event; nobody from Salvini’s party or advance team had asked for permission. Imperato had also been angered by the resulting online boycott campaign. He had always wanted his bar to be a place for drinkers, not for one side or the other. It was less an ideology than a business strategy. Shortly before Salvini’s planned visit, a local television journalist asked the pub owner for his thoughts.

“We don’t want to be the playing field for any politician,” Imperato told the journalist. “Salvini will come to my pub? Then it is likely we’ll be closed for festivities.”

It was the second part of that quote that was used in headlines.

A second backlash followed, this one much fiercer than the first, and hundreds of angry comments filled the pub’s usually dormant Facebook page, including one from a local League party official who accused Imperato of “discrimination.”

Imperato said it felt like being in a “car accident,” so much jarring back and forth, and the worst thing about it was that he’d only talked about closing down “in a moment of anger.” In reality, Imperato said, he intended to treat Salvini like any other customer.

“I have no problem letting anybody in, as long as the person pays and behaves fairly,” he said.

Salvini arrived around 6:45 p.m., and he was tired. He’d initially listed the event as a meeting with citizens inside the pub. But amid the controversy, he seemed to settle on the outdoor speech as a substitute. Salvini came to Mr. Brown for something smaller — a quiet sit-down with a few local dignitaries, some League activists.

The group grabbed a back table. Francesco Brusca, 37, who calls Salvini the “last hope for Italy,” was among them and said the politician just needed to restore a bit after a busy day in the cold.

Forty-five minutes later, after some pizza and a Peroni, Salvini was gone. But even when Imperato shut down that night, he was still thinking about what had happened. His stomach, he said, was “in shambles.” He tried to read the comments on the pub’s Facebook page but couldn’t handle it for long. He wondered: Had any fake accounts been fanning the flames? Would his business be damaged? Was it possible, with so much fighting, not to take a side?

“The very basis of my work is being unbiased,” he said.

Salvini, meanwhile, left the pub that night and headed down the street to another bar — one where he was more openly welcomed. Then it was on to dinner, and on to the next day, and on to the next towns, including one in the same region where Salvini had scheduled a “breakfast with citizens” at a coffee shop. This time, when the event was supposed to start, the coffee shop owner was at the door. He told an Italian newspaper he didn’t want to be a “megaphone for anybody.”

He barred League supporters from entering.