In a letter to Mexican bishops last month, Pope Francis called for a revisiting of the country’s history, especially the role of the Roman Catholic Church, and urged clergy members to “recognize the painful errors committed in the past.”

Yet it wasn’t in Mexico where his remarks drew controversy, but in Spain, where the right wing soon rallied behind the country’s role in conquering the Americas, alongside the church, more than 500 years ago.

Isabel Díaz Ayuso, the conservative leader of Madrid, said she was surprised that “a Catholic who speaks Spanish would talk that way,” adding that Spain had brought “civilization and freedom” to the Americas. And a former prime minister said he was proud of the conquest.

The reactions, on the eve of Spain’s celebration of its version of Columbus Day, were less about history and more about Spain’s current political moment: Just how far should the country’s conservatives tilt toward nationalism in attempting to boost their popularity?

It’s particularly troubling in a country that is still burdened by the not-so-distant memory of Francisco Franco’s dictatorship. Franco ruled until his death in 1975, stoking nationalist sentiment with hallowed symbols like the cross, the flag and bullfighting.

Ms. Ayuso’s Popular Party was founded decades ago by politicians from the Franco regime who wanted to turn over a new leaf. They treaded carefully when it came to nationalism, wary of any accusation of a return to the past.

José Manuel García-Margallo, who served as foreign minister in the Popular Party government in the mid-2010s, said the party had to hold the middle ground or risk losing its way.

“This is our mission now: to get back to the center,” he said.

The recent rhetoric from the right has the attention of politicians on the left, who say they fear the conservative center in Spain is becoming more extreme, much like the momentum that brought Brexit and Donald Trump into the conservative mainstream in Britain and the United States.