And his name is often invoked because he's such a fringe extremist. I doubt even 5% of Americans would agree with him, much less the ~40% who identify as right-leaning as you seem to imply.
It does not really matter whether those ~40% would agree. It only matter what portion of those would vote for someone who does. As a floor for that number I would submit that the Freedom Caucus has 32 of the 198 Republican seats in the house (~16% or Republican seats). Those Representatives have pretty much declared that they agree with him. So some percentage above that.