Anyone is free to pay more tax than the legal minimum. For that matter, Clinton absurdly receives $191,000 annually in presidential retirement subsidies -- though Clinton is a multimillionaire who does not need the money and is not retired! If Clinton feels he is insufficiently taxed, he could simply tear the annual $191,000 check in half and cause that amount to remain in the Treasury.
Any wealthy person who claims to favor higher taxes on the rich should voluntarily donate to the Treasury whatever additional amount he or she believes the rich should pay. For Clinton, or any wealthy person, to proclaim a willingness to be taxed more but then not voluntarily tax himself, is self-promotional hypocrisy. Clinton and other rich people who make claims about favoring higher taxes on the wealthy, but then hoard their money, want to be admired for seeming to be willing to sacrifice -- without the annoying complication of actually making any sacrifice.
--Gregg Easterbrook, ESPN.com, on manufacturing your own higher tax rate