Mid-July is peak season on the central Maine coast. The blueberries — the small, low-bush kind long prized by the state’s jam makers and pie bakers — had started to appear in the farmers markets, along with the first of the tomatoes. Bright orange tiger lilies burst from front yards, while Queen Anne’s lace and goldenrod line the two-lane roads. The summer light dazzles, falling in soft waves upon the spruce and cedar, and brightening the paint on both midcentury saltboxes and grander Victorian homes. It’s no wonder that people want to come here.

Stonington is, without a doubt, one of the prettiest towns on the Maine coast. Over breakfast one morning at Stonecutters Kitchen, I asked Linda Nelson, the town’s economic and community development director, how many Hallmark movies had been filmed there.

“Not enough,” she replied.

Stonington also happens to be the largest lobster port in America. Dozens of fishing boats are anchored in the harbor, while lobsters caught in nearby Blue Hill and Jerichoare exported across the country and, more recently, across the globe. I was told by locals that not one of the beautiful wooden homes that form Stonington’s classic picture postcard view is owned by a fishing family, who now live elsewhere on Deer Isle or over the bridge on the mainland. From the perspective of a lobsterman, many of whom have deep Maine roots, the P.F.A.s — People From Away, as locals call them — are a presence to be tolerated. The lobster fishermen and the tourists and part-time residents coexist in two separate worlds, one that is changing beneath the surface.

In a significant political year, when a small group of voters in a few places will most likely shape the answers to pivotal questions about our government, how does a community living out climate change feel to its residents? This part of Maine is represented by a Democrat in Congress, but the district, Maine’s second, has voted for Donald Trump twice by decent margins; this is one of those places where every vote can matter. Here, the punishing demands of the present, how hard everyday work is, how important costs and prices are, make the pivotal nature of this time feel very distant from politics.

During much of the past two decades, record numbers of lobsters have been caught off the Maine coast, providing a steady living for scores of lobster fishermen and their families. But a host of recent pressures has been building up that may upend a way of life that, for some, stretches back for generations. Indeed, as far as climate change goes, Maine’s lobster fishing community may well be America’s own canary in the coal mine.

“Everything has changed. Everything is changing,” said Dana Black, age 50, who is a fourth-generation fisherman and lives with his wife and two daughters over the bridge in Brooksville. “That’s all I’ve done,” he said. Mr. Black got his first job, on a lobster boat, when he was 12. By the time he was in high school he had gotten a taste of what kind of money could sometimes be made on the water. He skipped school one Friday to work as a sternman on an offshore boat, hauling lobster traps. By the time he got back on dry land on Monday, he recalled, “I had made 27-hundred bucks.” Like his father, grandfather and great-grandfather before him, Mr. Black had found his calling.