But Mr. Mitsotakis, in a televised debate this month, conceded that Mr. Androulakis should not have been wiretapped. The spying was an especially bad idea, it turns out, because Mr. Androulakis’s support may prove pivotal to the election’s ultimate outcome.

Yet the scandal is way down on voters’ list of priorities, as is Mr. Mitsotakis’ treatment of migrants.

John Vrakas, 66, who was handing out fliers for Mr. Tsipras across from the square where Mr. Mitsotakis was due to speak, shrugged that Europe didn’t seem particularly bothered as long as the prime minister assuaged their concerns on the economy and Ukraine. “It’s a kind of trade,” he said.

It is one that Greek voters seem happy to make.

As Mr. Mitsotakis walked the streets, a bus driver reached out the window and clasped his hand. “Supporters until the end,” chanted a group of men in front of a cafe. “We trust you,” a woman shouted from her jewelry shop.

What “resonates in Europe,” Mr. Mitsotakis said, was that his was an “anti-populist government” that had brought much-appreciated stability back to Greece in a rough region.

He got up from the interview in a small and otherwise empty restaurant, and shook more hands on the way to the square, where he launched into a short stump speech interrupted by chiming church bells.

“I’m not sure who they are tolling for,” Mr. Mitsotakis exclaimed, “but not for us.”