The photograph or audio recordings weren’t available until something like the end of the 19th century, so the tactic of introducing questionable ones wasn’t even necessary until then; you could just claim that someone said or did whatever prior to that point.

I know that here in the US, politicians being accused of saying one thing in campaign speeches in one place and another thing in another were part of what went on, since there wasn’t a reliable way of proving what they said in one place. I expect that people will figure out ways to deal with things.