Based on what, though?
For example, this chart shows that the deaths in Gaza markedly increased in the first year of Trump's term. While Biden and Harris obviously didn't do near enough to try to stop Israel, Trump openly encouraged them to finish the job, and I think that attitude and brazen support contributed to that increase in deaths.
This is just another way of stating, contrary to the evidence, that Harris would have somewhat mitigated the worst of the genocide. If your goal is to stop the genocide, Biden whole-heartedly supporting Israel while observing the formalities of democracy is no different than Trump whole-heartedly supporting Israel while gerrymandering. Republicans keeping Democrats out of power doesn’t make a difference if Democrats are going to rain mass slaughter down on the world, too.
My point is that while the odds are still not great, we have better odds of making the democrats change course than the republicans, especially since so much of the anger with Israel stems from the democrats' base, not the republicans. By allowing republicans to solidify their position, we allow the most difficult to persuade party to secure long term power. We should do all we can to buy time and nudge the odds of success in our favor because it probably won't be any one factor that finally stops it, but a confluence of factors that all add up to enough to break the damn. Republicans are a completely lost cause on this subject, but there's a nonzero chance the democrats can be broken.