A “relative bang for the buck” quantitative way to think about giving money to a candidate (actually any investment at all) is as follows (this is not fully thought out, and I suspect it is how some people intuitively make their decisions): what is the ratio of the correlation between the amount of money I and similar others give with the policies of the candidate, relative to the same ratio for other donors?
If I give $100 and you give $200, then on our points of different we can reasonably expect to influence the candidate in a ratio 1:2 or to see those policies in the platform. We can look at this either cumulatively (candidate’s current policy) or dynamically (how does the policy change in proprotion to how much I’ve given).
Of course I don’t have the “data”, but to me it seemed that Sanders’ policies (or those of the progressive candidates I support) are in very good alignment with my principles and those of the other supporters. Similarly, it should be pretty clear that Biden’s and the Democratic party’s corporate donors get almost absolute bang for the buck relative to what progressive donors currently see or can expect to influence. Biden simply does not reflect our values as much as he does those of big corporations.
Of course the same relative ratio is even worse for Trump, that makes it even less likely that I’ll donate to Trump, but not more likely that I’ll donate to Biden, I’ll keep my money in cash and donate down ballot.