BUENOS AIRES — From a distance, our political story this year seems simple: Good pro-market guy loses, bad guy wins and populism comes back. It is not.

Until the final vote in October, Argentina in effect has a virtual president-elect, the opposition candidate Alberto Fernández, and a lame-duck president seeking what has become an unlikely re-election, Mauricio Macri. Unlike the leaders who have recently been elected in Latin America, Mr. Fernández is a moderate. But he will face an uphill battle to remain that way.

Mr. Fernández unexpectedly outperformed President Macri by a margin of more than 15 percentage points in a preliminary contest last week meant to weed out the least popular candidates. (In addition to Mr. Fernández and Mr. Macri, four politicians have qualified to compete in the October vote.) Mr. Fernández’s running mate is former President Cristina Fernández de Kirchner, which has raised concerns about a return of a so-called populists who dominated Argentina until 2015.

But Mr. Fernández and Mrs. Kirchner are not one and the same. Argentina is a strong presidential system . The person in that office has an ample margin to get his way over institutional and political checks. Mr. Fernández is a pragmatist whose political principles lean to the center-left, and who has no qualms when it comes to picking the policy tools to pursue them .