Is it mere coincidence or the beginning of a trend? First, former president Bill Clinton co-writes a potboiler (with some guy named James Patterson) about an embattled Democratic president with a kick-ass résumé (Army Ranger, POW, minor-league baseball player and loving single dad) who saves the United States from annihilation. Now, former president Barack Obama and former vice president Joe Biden have been reimagined as a dynamic detective duo in a thriller about the opioid epidemic called “Hope Never Dies,” by Andrew Shaffer. If, in the next year, Jimmy Carter surfaces as either the author or the star of a suspense novel, we’ll know we’re witnessing the emergence of a fad in which Democratic former presidents and vice presidents return to fix — in fiction — a world gone wrong.