663
"Contrary to a 'horseshoe' theory, the evidence reveals increasing antisemitism moving from left to right."
(64.media.tumblr.com)
Hersh, Eitan; Royden, Laura (25 June 2022). "Antisemitic Attitudes Across the Ideological Spectrum" Political Research Quarterly.
doi:10.1177/10659129221111081
I don't know that I agree with your definition of extreme. On the one hand, there's popularity of various ideas, and on the other, there's how much the idea differs from the way things are currently done. It's possible for an idea drastically different from the status quo to be popular, but it would still be considered extreme because of how big of a change it would be.