Senator Susan Collins and challenger Troy Jackson are fighting for a Maine Senate seat while highlighting their roots in Aroostook County. Both candidates grew up in this isolated region, which shaped their political views. During Thursday’s debate, Collins said, "I helped out in the fields during harvest breaks from school."

The story of northern Maine is the story of rural America: Fewer jobs, a declining population and a deeply ingrained feeling of being forgotten, or looked down upon, by the liberal population centers calling the shots.

That sense of alienation helped fuel the rise of President Trump. It has also shaped the critical U.S. Senate contest in Maine, where both candidates -- Senator Susan Collins, the Republican incumbent, and Troy Jackson, the Democratic challenger -- grew up in Aroostook County, a vast wilderness bordered by Canada on three sides and defined by its geographic isolation.

Each candidate refers often to their roots in "The County," as Mainers know it. During their final debate on Thursday night, responding to a pointed question from Mr. Jackson about her respect for working-class voters, Ms. Collins again noted her Aroostook County roots and her first job there picking potatoes.

Ms. Collins, 73, first won her seat in 1996. By now, almost everyone in Maine knows that she helped out in the fields during harvest breaks from school in Caribou, where her ancestors founded a lumber business in 1844.

But it is Mr. Jackson, a fifth-generation logger who grew up poor in the remote St. John Valley, who is trying to ride the populist wave that first lifted Mr. Trump.