BAGNÈRES-DE-BIGORRE, France — In the final days before France’s presidential election on Sunday, Emmanuel Macron was tramping through the snow high in the mountains near the Spanish border for a critical campaign stop near this tiny village where his grandparents once lived.

With the race exceptionally tight, it seemed an unlikely place for any candidate. Hardly a voter was in sight. Instead, what Mr. Macron later described as a “pilgrimage,” with some 20 journalists in tow, was in part intended to show his human side, to reflect his connection to a “terroir” — a definable place and personal history — that French voters could latch onto.

With no political party to speak of, and never having held elected office, Mr. Macron, 39, a onetime investment banker and former economy minister, is leading an improbable quest to become modern France’s youngest president. His profile is that of an insider, but his policies are those of an outsider. If the ever-precocious Mr. Macron is to succeed, his first challenge is to sell a product still largely unfamiliar to almost everyone: himself.

That Mr. Macron is such an unknown underscores his unusual position in a French election that, to some degree, is a referendum on the future of Europe. The far-right leader Marine Le Pen threatens to take France out of the European Union. By contrast, Mr. Macron is ardently pro-Europe and has portrayed himself almost as the anti-Le Pen.