In 1860, Virginia's Democratic Rep. Albert Jenkins introduced an amendment to eliminate the presidency and instead elect two people to share executive power. While that may seem weird to us now, the idea of a singular presidency was actually quite controversial even before the Constitution was put to paper. As you might imagine, American colonists who'd just thrown off one king weren't too excited about giving another a place in their new government. But thanks to defenders like Alexander Hamilton and James Madison, the idea of a lone executive ended up in the Constitution and has remained the law of the land ever since.
So why did Jenkins bring it up again some 80 years later? Slavery. See, with the election of Abraham Lincoln, southerners started to worry that a northern president might not have their best interests at heart, particularly when it came to slavery. A dual executive, however, would almost certainly give someone from the South a voice in the nation's highest office.
The idea popped up again in 1878, this time from a northerner. Ohio Rep. Milton Southard felt that the president was becoming too much like a king and, in response, he proposed a three-part executive council consisting of representatives from the eastern and middle, western, and southern regions. His plan, of course, went nowhere, but that hasn't stopped people from calling the president a king even to this day [source: Vile].