Seems it was “made up” while he was still doing it...during his first term. That makes it history.
It was made up.
“The claim that Thomas Jefferson had a sexual relationship with Sally Hemings began with James Thomson Callender, a notorious journalist and scandalmonger. Callender had demanded that Jefferson, who was elected president in 1800, appoint him postmaster of Richmond, Va. At one point during the summer of 1802, Callendar shouted from in front of the White House, “Sir, you know that by lying [in press attacks on President John Adams] I made you President!”
When Jefferson refused to make the appointment, Callender promised “ten thousand fold vengeance” and wrote a series of articles denouncing Jefferson as a French agent and an atheist. When those charges had no effect, he insisted that the president had taken a young slave girl to be his “concubine” while in Paris during the late 1780s. At the time, Sally attended to Jefferson’s young daughters, who lived in a Catholic boarding school across town in Paris that had servants’ quarters. She didn’t live at the Jefferson residence.
Both John Adams and Alexander Hamiltonpolitical rivals of Jefferson’s at the timerejected Callender’s charges, because they knew Jefferson’s character and had bitter personal experiences with Callender’s lies.
The case against Jefferson was the subject of a yearlong examination by a group of 13 distinguished scholars, including historians Robert Ferrell (Indiana University) and Forrest McDonald (University of Alabama), as well as political scientists Harvey Mansfield (Harvard) and Jean Yarbrough (Bowdoin). Save for a mild dissent by historian Paul Rahe (now at Hillsdale College) the group concluded that the story is probably false. This Scholars Commission, which I chaired, published its findings in book form late last year.”
http://www.wsj.com/articles/SB10001424052702304211804577500870076728362