Abraham Lincoln and Stephen A. Douglas of Illinois (1860). Ronald Reagan and Richard Nixon of California (1968). Hubert H. Humphrey (1968) and Eugene McCarthy (1972) of Minnesota. John Lindsay and Shirley Chisholm of New York (1972). Pete DuPont and Joe Biden of Delaware (1988). Paul Simon and Jesse Jackson of Illinois (1988). Jeb Bush and Marco Rubio of Florida (2016). Kirsten Gillibrand and Bill…