As nouns the difference between leftism and rightism
is that leftism is belief in the principles of left-wing politics while rightism is (uncountable) Belief or support of he principles of the political right.
leftism
Noun
Belief in the principles of left-wing politics.
rightism
English
Noun
(
en noun)
(uncountable) Belief or support of he principles of the political right.
(countable) An act or statement supporting the political right.