The supposed statement from Clara Harris first appeared on page 1 of the 16 April 1865 edition of the
New York Herald:
It's coupled with a supposed statement from Mary Lincoln that she initially thought Booth jumping to the stage was her husband falling to the floor.
If you note the date, the
Herald article was printed the day before Rathbone and Harris gave their affidavits which completely contradict this. The only really persuasive way to explain this is that the
Herald article has to be some type of newspaper hoax to get a "scoop". Why they would do this (or at least such an easily verifiable hoax attributed to Harris), I don't know.