SPARTANBURG, S.C. >> The Republican Party’s tug-of-war over its relationship with black and Hispanic voters was under way long before Pope Francis decided to answer a question about Donald Trump.

On one side, Marco Rubio and others insist the GOP must attract more minorities to win the presidency. On the other, leading rivals Trump and Ted Cruz embrace fiery rhetoric designed to motivate angry white conservatives. Complicating it all is immigration, the issue the party’s pragmatic professionals can’t square with the passions of their most faithful voters.

Pope Francis on Thursday shined an international spotlight on the intra-party debate when, asked about Trump’s call to build a massive wall on the U.S.-Mexican border, he said those who seek to build walls instead of bridges are not Christian.

It’s a high-stakes clash that could determine much more than South Carolina’s Republican primary election on Saturday, but also whether the GOP nominee succeeds in November’s general election.

“I don’t think conservatism has ethnic boundaries,” Rubio told The Associated Press on Thursday as he campaigned alongside South Carolina’s Indian-American Gov. Nikki Haley and African-American Sen. Tim Scott.

“We just need to take our policies to people that haven’t regularly voted for us in the past, communities that would benefit from what we stand for, but perhaps have been told that Republicans don’t care about people like them,” he said.

Haley highlighted the diversity on stage with Rubio, the son of Cuban immigrants, during an earlier rally in West Columbia: “A new group of conservatives that’s taking over America looks like a Benetton commercial,” she said. She added, “I hope we’re the new faces of the conservative movement.”

Yet their day on the trail was overshadowed by Pope Francis’ extraordinary reply to a question about Trump and his focus on building a wall on the U.S.-Mexico border to stem illegal immigration. “I say only that this man is not Christian if he has said things like that,” Francis said.

While the question concerned Trump, who described Mexican immigrants as rapists and criminals in his announcement speech and later called for a temporary ban on all Muslims entering the United States, the billionaire real estate mogul isn’t alone in his calls to build a border wall.

Cruz supports the idea, too, and Rubio has repeatedly said that no progress can be made on immigration until Washington can prove to Americans that illegal immigration is under control. “They want to see the wall built,” Rubio said of voters at the last GOP debate.

That border-security-first approach is at odds with the recommendations of the Republican National Committee, which determined after an exhaustive post-2012 study the GOP must adopt “comprehensive immigration reform” to help expand its appeal beyond older, white men in order to again win the White House.

It may not matter in South Carolina’s primary, a contest that will be dominated by white voters. In 2012, the state’s Republican primary electorate was 98 percent white.

It’s a different story for the November general election, when minority voters are expected to make up more than 30 percent of the eligible voting-age population — and more than 50 percent of the voter pool by 2052.

A new Associated Press-GfK poll found that Rubio and Cruz are slightly more popular than Trump among Hispanics, although none of them is well-liked. All of them have especially low ratings among blacks.

Fifteen percent of blacks and 31 percent of Hispanics have a favorable view of Rubio, the new poll found. Cruz earns positive marks from 11 percent of black voters and 29 percent of Hispanics, while Trump finishes at the bottom with favorable ratings from just 8 percent of blacks and 16 percent of Hispanics.

Trump isn’t ignoring minority voters. He’s campaigning in South Carolina this week alongside Pastor Mark Burns, a black televangelist who told AP that many people have the mistaken impression that Trump is “a racist bigot.”

“That’s not the case at all,” he said.

“We’ve changed thousands of African-American’s mindsets,” Burns said.

Cruz, whose father is also a Cuban immigrant, is banking on winning the White House by energizing evangelical and working-class white voters. To help excite them, Cruz has brought along allies to South Carolina this week that include Iowa Rep. Steve King, who has compared immigrants living in the country illegally to drug mules and livestock.

Cruz was to spend Friday, the day before the South Carolina GOP primary, flying around the state with “Duck Dynasty” star Phil Robertson, who has said that African-Americans were happy under Jim Crow laws.

Republican National Committee member Henry Barbour, who helped author the RNC’s post-2012 study, praised the minority outreach efforts of candidates like Rubio and former Florida Gov. Jeb Bush.

“But it’s troubling to me for the future of our party that we have candidates like Donald Trump and Ted Cruz who think that it’s still 1972,” Barbour said. “Not only is it an electoral loser, it’s bad for the country.”

Associated Press writers Scott Bauer in Greenville, South Carolina, Jill Colvin in Kiawah, South Carolina, and news survey specialist Emily Swanson in Washington contributed to this report.