Actually, that's been the case for just about exactly 16 years. I watched it happen in real time.
I went through a libertarian phase in the 80s and 90s, mostly because I couldn't reconcile my anarchist sensibilities with the fact that humanity just isn't ready to do entirely without authority. I eventually just gave in and shifted to anarchism, since it's really the only position that's consistent with my principles, and I just treat it as more of an ideal toward which to strive than an actual immediate goal.
In any event, I knew the libertarian movement of the era. It was more right- than left-wing even then, but it was primarily libertarian, exactly as the term implies - primarily focused just on minimizing political authority.
Then came the Tea Party.
The first Tea Party protests were organized by actual libertarians and were specifically against the Wall Street bailouts in the wake of the 2008 financial crisis that Wall Street had essentially single-handedly caused. And notably, they were against the Bush administration.
But then, shortly after Obama's victory, with a suspiciously well-timed and widespread boost fron the legacy media reporting on an even more suspiciously well-timed on-air comment by Jim Cramer, the Tea Party was recast into a Republican protest against the left. And it almost immediately transformed from a series of protests against the Wall Street bailouts to a traveling right-wing carnival of hate. (And conveniently enough, the focus on the Wall Street bailouts completely vanished).
While I saw that happen I didn't recognize the near-immediate Overton Window shift it triggered until I noticed a sudden influx of libertarians on anarchist forums. And they all had the same story - they had abandoned their libertarian forums because they had been taken over by angry, stupid Republicans.
And that became the status quo. The former libertarians mostly settled into their own sub-community of "anarcho-capitalists" and the libertarian movement is now pretty much just angry, stupid Republicans who are only marked out by the fact that they lean more into corporatocracy and militarism than religious fundamentalism and social war.
