Yale law professor and novelist Stephen L. Carter has an unlikely heroine to the Cuban missile crisis in his new novel: Margo Jensen, a 19-year-old black college student, making her way into heady White House politics in “Back Channel.”

He was surprised, when he was finished, at how much she resembled the heroine in his previous book, “The Impeachment of Abraham Lincoln.” In that book, Abigail Canner was also a black young woman caught up in White House intrigue beyond her years.

“I was utterly unconscious of it,” he’s saying on the phone, chatting from his New York hotel room in the midst of book tour. “Their physical descriptions are very similar, which I had overlooked. Both are young black women, well educated, moving in spheres they wouldn’t be expected to be in. Both have parents dead, raised by strong women…I didn’t set out to write the same character twice. But it did, in a sense, work out that way.”

The 59-year-old D.C. native will be at Politics and Prose to talk about the book — and some lessons for the U.S. and Russia today, as tensions again have flared between the Cold War rivals.

But for the most  part, Carter is again focused on mixing historical fact and fiction in Washington politics. The city plays a central role in many of his novels, perhaps most famously in his best-selling debut, “The Emperor of Ocean Park.”

In “Channel,” the story began to take shape in his mind when reading Robert Dallek’s biography of John F. Kennedy, which disclosed that Kennedy had an affair with a 19-year-old intern. Carter decided to parlay that affair into a fictional cover story: What if there was no affair, but the relationship was to hide a secret back channel of communicating with the Kremlin during the crisis in Cuba? And what if the young woman was black, not white? It’s not quite as far-fetched as one might think — there really was a back channel of communication, but it was through ABC newsman Jack Scali. His real-life Russian counterpart was Aleksander Fomin (real last name, Feklisov), who appears in the book.

“I did a lot of investigating for Fomin,” Carter says. “I gave him a completely different background and gave him much better command of English than he had in real life.”

More difficult to portray was the 35th president. Carter went back to tapes and listened to the patterns and style of Kennedy’s speech in order to get the syntax and patter. In the alchemy of historical fiction, the idea is to get the real people to sound real…even when what they’re saying isn’t.

“If I was inventing words to put in his mouth, I wanted it to be plausible, like I did with Lincoln, that he might have said these particular words.”