A New Yorker article [that I haven't fully read] describes the legs this word has.
Think about it: it's a very convenient excuse.
If I misspeak, then it's not necessarily a lie. It means that I knew the truth, but somewhere between my mind and my mouth it wasn't articulated You cannot really criticize someone for a daffy idea when they misspeak, as it's not necessarily representative of their views.
And now that a couple politicians have used it somewhat successfully, it'll be all the rage for a long time.
Keep your eyes out for it and you'll notice it.