>> so help me god. >> reporter: but he's also rewriting unspoken rules and road maps largely designed by men for women. >> there's a library at the residence where we live, and it's i think every single book ever written by a vice president about a vice president about the vice presidency, and our favorite one's title is "vice presidents and second ladies." and think about it. we're going to need a new book because there's now a man in this role, and i say half jokingly i may be the first, i better not be the last. >> what do you think that sort of title or the headline of that book should be? >> it should not even be a big deal that i'm a man going forward. we need to have more women in leadership. there needs to be more women in government, more women in the business world, more women in communications. more women in the military, you name it. so i want to be in a world where this is not unique.