There are some very liberal GOPers.
They can rightly be called RINOs.
They can almost be counted on to caucus with the libs.
With the exception of Harding (2 years), Coolidge (6), Goldwater (close, but no cigar), and Reagan (8), the progressive (left) wing of the Republican Party has been in charge for the past 110 years. I think they own the brand, bought and paid for.
Conservatives are the outsiders, so maybe the term
RINO applies more accurately to conservative and libertarian Republicans.