Scott S. Greenberger is the author of “The Unexpected President: The Life and Times of Chester A. Arthur.” (André Chung/for The Washington Post)

Scott Greenberger, 48, is a journalist and the author of “The Unexpected President: The Life and Times of Chester A. Arthur. He lives with his wife and two children in Takoma Park, Md.

What’s the most common response you get when you tell someone you’ve written a book about Chester Arthur?

You do get the occasional, Who? And you do get a lot of people who say, “Isn’t he the guy with the mustache?” He’s become known through the ages for that facial hair. I sort of tried to use his obscurity to my advantage. Hardly anybody knows anything about the guy.

What drew you to him?

I wanted to do something that hadn’t been done before, and he certainly qualifies. No one had really done a full-length biography of him since 1975. And I think the Gilded Age is a really interesting period and relatively unexamined. It is the period where you can detect the beginning of the country and the society that we know today. You had corporations and concerns about the influence of money in politics and rapid industrialization. And, of course, now people talk about us living in a second Gilded Age, and one of the things that happened then that is happening now is very dramatic income inequality. So I thought it was an interesting period to explore because of that parallel.

He was not particularly admired as a politician when he was selected as James Garfield’s running mate.

No, Arthur was a machine politician, a hack who ended up on the ticket for purely political reasons, and no one thought anything of him. If they thought about him at all they considered him to be unqualified for the presidency. And then Garfield was shot and Arthur became president, and he surprised everyone by embracing the cause of civil service reform, which, at the time, was the big issue in the United States.

Does he immediately redeem himself as president?

It’s sort of a gradual process. When Garfield was lying on his bed in agony, it had a profound effect on Arthur. It really shook him and made him reevaluate what he had been up to that point in his political career. And he really did begin to grasp the enormity of the job he was stepping into and the responsibility that he had not to just his faction of the Republican Party and not just to the Republican Party, but to everybody, to all Americans. He received a letter from a young woman in New York named Julia Sand, who was a housebound young woman and a political junkie, but this was when women weren’t allowed to vote or participate in any meaningful way in politics. And she wrote a letter urging Arthur to rise to the occasion, to be a better person and trying to make him see that now that this great office had been thrust upon him, he needed to be better. She urged him to return to his idealistic younger self, and these letters had a profound effect on him.

As a biographer, when you’ve spent months and years working on a subject, is it weird to be done with the book and have to end that relationship?

It’s a little weird. There’s a statue of him in Madison Square Park in New York City, and everyone passes it by, and no one notices it or pays attention. And I do feel like I have this strange connection with him through the ages. There aren’t many people who have delved into his life. Reading people’s personal letters is really a fascinating experience. It’s a strange sensation when you think about someone 150 years ago sitting down to write to their sister or best friend or fiancee, and here you are in 2017 reading over his shoulder. But it’s something that I really enjoy about the process.

Do you think Lin-Manuel Miranda could turn your biography of Arthur into a hit Broadway musical?

I could only hope. Obviously I’m biased, but it really does have compelling characters, larger-than-life characters. There’s violence and sex, and it has all the things that you think would be appealing to him, so I’ll just hope he reads this interview.

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