I think you're misunderstanding davmre's proposed model, which is
not about there being corruptible politicians and incorruptible ones. The idea, rather, is that even without corruption big donors can effectively buy influence, because what they do is to help politicians who (honestly, sincerely, without corruption) happen to share their goals.
So, e.g., suppose that before any money gets thrown around there are exactly two Democratic presidential candidates: Hillary Clinton (who loves Wall Street, just because she does) and Bernie Sanders (who hates Wall Street, just because he does). Then Wall Street donates a bazillion dollars to HC's campaign, she squashes BS like a bug with her superbly-resourced campaign, and becomes president. Since she (honestly, sincerely, incorruptibly) loves Wall Street, she uses all the power the presidency gives her to advance the interests of Wall Street. And, bingo, Wall Street has got what it wants by spending money, without any politicians being corruptible. In a parallel universe, Wall Street has no money to spare for political donations (that would eat into their bonuses, which would never do) and Occupy Wall Street donates a bazillion dollars to BS's campaign instead. Now he squashes HC like a bug with his superior campaigning firepower, becomes president, and makes banking a felony -- and, bingo, OWS has got what it wanted by spending money, again without a shred of corruption being needed.
Back in the real world, of course no one is incorruptible, and indeed I bet real-world-Hillary is influenced by all those donations, but it seems pretty plausible to me that the mechanism davmre describes is in fact at least as important as corruption in explaining why large donors make large donations.
(But I also agree with whoever it was that said any answer less definite than "no, of course I am not influenced" would likely be political suicide, and a policy of never voting for anyone who makes that claim is in practice probably equivalent to a policy of never voting for anyone who has large enough conflicts of interest for the question to be put in the first place.)