PARIS — The cover of Paris Match magazine late last year featured a handsome, 30-something man strolling arm in arm with an attractive blond woman in her 60s. The same couple were on the cover of a summer issue, holding hands at the beach, and on a spring edition dressed up for a state dinner.

As France gears up for presidential elections in April (and probably a runoff in May), this unusual pair could help prevent it from becoming the next country to succumb to xenophobic populism. He’s the upstart presidential candidate Emmanuel Macron, and she’s his former high school French teacher, Brigitte Trogneux, now his close adviser and wife.

Mr. Macron, the 39-year-old former economy minister, is now in second place in the polls. He surged past the conservative François Fillon this week thanks to “Penelope-gate” — an investigation into whether Mr. Fillon’s Welsh-born wife held a well-paid government job but didn’t actually work, and other allegations.

Mr. Macron still lags the front-runner, Marine Le Pen, who wants France to slash immigration and leave the European Union. Mr. Macron is adamantly pro-Europe and quickly opposed President Trump’s barring of refugees. Polls show that Mr. Macron would easily defeat Ms. Le Pen in a runoff.