WASHINGTON — The descent of the 2016 presidential campaign last week into the realm of sex tapes and marital infidelity was remarkable enough in its own right, but it also offered a reminder of what has been largely absent from the race: a debate about issues of public morality that for decades have been at the heart of the country’s political divide.

In a striking departure from the recent history of White House campaigns, there has been almost no discussion of abortion or gay rights, two of the most animating issues for millions of American voters.

“This is more about this year’s candidates than it is about the country,” said Russell Moore, the public face of the Southern Baptist Convention. “I don’t think America is as secular as this campaign would have you think.”

The country may get a reminder of that on Tuesday evening during the vice-presidential debate.

The two men who will face off, Senator Tim Kaine of Virginia and Gov. Mike Pence of Indiana, share a deep religious faith that is central to their politics, but has been obscured by a more profane than holy race on top of the ticket.