When one reviews the charges and countercharges that have characterized the 2016 presidential election campaign, one topic that’s been left on the fringes is faith. That changed on Tuesday night as two candidates whose faith is central to their political philosophies took to the debate stage.

It’s an argument, at its simplest, on the meaning of justice and mercy, Old Testament and New Testament, and how to live one’s personal faith.

For most of the debate, Christian charity was hardly visible — with lots of interruptions. But it quieted down and slowed down as both vice presidential candidates looked inward to what they believe and how it plays out in their policy positions.

Republican Gov. Mike Pence of Indiana was raised Catholic but later became an evangelical Christian. That brings balance to the GOP ticket and reassurances to an evangelical base that had been skeptical of the thrice-married Donald Trump — who came late, and sometimes shakily, to their causes.

Democratic Sen. Tim Kaine of Virginia is an old-fashioned social justice Catholic, formed in large part by his missionary service in Honduras as a young man. He has been known to name-check Jesuits and Pope Francis. The Catholic vote swings powerfully in presidential years, often in the direction of the eventual winner. Hillary Clinton, at the top of the ticket, has been sure but not quite as vocal about her Methodist upbringing.

The sincerity shone through when Pence versus Kaine turned to God, no matter what house of worship the viewer does or does not attend.

It was fascinating to learn how two men, quite strong in faith, could have their beliefs lead them in such different directions. It was the social conservatism versus social justice debate that sometimes divides attendees in the same house of worship. And it is illustrated not just on issues such as abortion and same-sex marriage, but on climate change, health care and the economy.

On Tuesday, when asked about their struggles when balancing personal faith and policy, Kaine, a former Virginia governor, raised the issue of the death penalty, which the Catholic Church is against.

And “so am I,” he said. “I had to grapple with that.”

Kaine said that while it was difficult to allow executions — legal in his state — to go forward, he told the Virginia voters he would uphold the law, “and I did.”

“My Christian faith is at the very heart of who I am,” said Pence. And while he said he respected Sen. Kaine’s “sincere faith,” Pence added that his own compassion for the “sanctity of life” had affected his policies in Indiana — in favor of health care counseling and non-abortion alternatives, such as adoption. He quoted the now sainted Mother Teresa and said he was proud to stand with Trump on a pro-life ticket.

“Society will be judged by how it defends its most vulnerable — the aged, the infirm, the disabled, and the unborn,” Pence said.

Kaine asked, “Why don’t you trust women to make this choice for themselves?”

In a debate when much was lost in cross-talk and questions that were often disjointed, Democratic and Republican positions on this one issue were clear. One candidate and one ticket supports Roe v. Wade and the other opposes it — and each presumably would appoint judges to reinforce that view.

Though it is not clear that Tuesday night moved many voters, Pence and Kaine no doubt strengthened the votes of their respective bases, and mentioned — if only briefly — issues of how life is lived that have been missing so far. At least the conversation was a welcome respite from talk of infidelity and sex tapes.

Roll Call columnist Mary C. Curtis has worked at The New York Times, The Baltimore Sun and The Charlotte Observer. Follow her on Twitter @mcurtisnc3.