George Washington: "Few men have virtue to withstand the highest bidder"
And that's why the Constitution contains the emoluments clause.
The emoluments clause, however, does not require direct proof of anything untoward, and that is essential to its effectiveness. The most powerful anti-corruption rules are prophylactic, forbidding a whole category of relationships that are likely to lead to corruption.
Consider the countries we know are making payments to Trump companies through state-owned entities, payments that affect Trumps wealth: China and the United Arab Emirates, both at the heart of regions critical to U.S. foreign policy. Then consider the longer list of countries in a position to benefit him because of business relationships Trump has, including India, Indonesia, Turkey, the Philippines, Great Britain and Vietnam. This is just a beginning sketch of what we know so far; Russia, Saudi Arabia and Taiwan reportedly may also be involved with Trump businesses. The benefits come from a range of relationships: The Qatari state airline pays rent at the Trump Tower in New York; entities in Britain, Bulgaria, Brazil, Indonesia and Vietnam reportedly make licensing payments for the rights to produce local versions of The Apprentice, Trumps reality TV show; his developments in India require governmental permitting, which under the law would be a forbidden benefit.
Each of these countries, and possibly more, now has a direct mechanism to attempt to influence the president. Whats more, every time Trump makes a foreign policy decision that relates to any of these countries, citizens will wonder whether he, like Charles II, put his own financial interest ahead of American jobs, or whether he is engaging in or refraining from military action because of a business relationship.
Trumps lawyers made a strange concession in a news conference recently, announcing that Trump would donate all profits from foreign government payments to Trump hotels to the U.S. Treasury. The suggestion was that the donation mooted the problem. But another unspoken implication was that there is something troubling about foreign-derived profits. The donation does nothing to address the Constitutional violation, which occurs at the moment of accepting the benefit, even if Trumps hotel loses money on the transaction. It merely means that some of his constitutional violations will be followed by a payment of penance. Moreover, profits from the hotels represent only a part of the foreign benefits that are flowing to him none of his office towers, condo or apartment sales, licensing agreements or loans on other properties are covered at all.
https://www.washingtonpost.com/posteverything/wp/2017/01/26/trump-is-getting-payments-from-foreign-governments-we-have-no-idea-what-they-are/?utm_term=.7b71f389c7f4