I'll go first. I had a take that if you see a bunch of advertisements saying to vote no on prop x, and nearly none saying yes on prop x, you should probably vote yes. Because if big money is behind an effort to sway towards no, there's probably corruption in the ranks.
I think it depends on what the fascism is against.
Communism? Yes, they would.
Socialism? I don't think so, but I could be wrong.
Social democracy? I think they would just bite the proverbial bullet and support this.
When Allende came to power in Chile he came to power as a democrat first and foremost. He was a Marxist but he emphasised again and again he held democracy high and that he was merely representing the factions of the left which had united
When Castro told Allende (referring to the counter-revolutionary feeling developing amongst the right/the military and traditionalists) to "get these people under control" Allende instead insisted he had found a 3rd way between the Dictatorship of the Proletariat and capitalism
https://www.nytimes.com/1972/12/17/archives/the-opposition-in-chile-said-castro-to-allende-if-you-dont-get.html
Marx and Engels developed the theory of the Dictatorship of the Proletariat and why Marx famously remarked they'll be "no apology for the terror". Because if you walk up to the bourgeois meekly bowing your head and asking politely for reforms they'll do what they did in Chile - run a ruthless dictatorship of the bourgeois in which people are disappeared, executed and incarcerated for having ever walked on the same side of the street as a communist/socialist or trade unionist
Perhaps I should have clarified, I was more talking about rank and file type voters who would consider themselves more "liberal" than "conservative", not liberals who are wealthy and/or powerful.