The Democrats are mostly utilitarian liberals, but 'leftist' activists are increasingly dominated by constructionists, and they either wish to coerce the Democrats into agreeing with them, or else try to boycott the Democrats when they don't get their way (like with this election, it seems some of them really don't mind four more years of Trump because Harris is too moderate for them anyway). The Republicans used to be a combination of organicist conservatives and reactionaries, but lately the reactionaries are gaining dominance and driving away the organicists, which is worrying.

p.s. far-left positions include cancel culture, oppressor vs. oppressed identity politics, almost everything is a social construct, attempts to radically and inorganically change language, etc. These are not generally supported by mainstream Democrats, but are embraced by many 'leftist' activists.