This is it. You can do harm reduction in voting for the least-worst feasible candidate, while organising/protesting on issues you disagree with them on.

E.g. In the UK, Labour is often poor on queer rights issues, but comparatively massively better than the tories/reform would be, not to mention economic and welfare policies. So I vote Labour, and attend pro-trans rights protests and criticise Labour and their stance on this issue.