I used quotations around the term bribe for a reason. By definition, if it's legal, it's not a bribe although it may walk like a duck and quack like a duck. One of the issues is an incentive problem: those who have the power to make it illegal are also those who benefit the most from it being legal.

>Unless we want to make political donations illegal

I think this is displaying dichotomous thinking. There's a lot of room between a political donation free-for-all and making political donations illegal. In between there are many proposals for a more mitigated approach. One being Lessig's idea of "Democracy Vouchers"[1]

[1] https://en.wikipedia.org/wiki/Republic%2C_Lost#Democracy_vou...