Foreign diplomats are flocking to his Washington hotel, down the street from the White House, to spend money and curry favor with the administration. The president continues to rent space in Trump Tower to a Chinese government-owned bank and an agency of Abu Dhabi.

Regulators in China, a market that Mr. Trump has long sought to break into, just gave his business 38 valuable trademarks in a process that was unusually speedy for a trademark application. To make matters — or at the very least appearances — worse, this occurred after Mr. Trump toned down his harsh talk toward Beijing.

How can Americans trust that policy has been unaffected by profits, when Mr. Trump’s travel ban did not affect any of the countries where he has business interests? Possible conflicts are everywhere. Mr. Trump recently directed the Environmental Protection Agency to roll back regulations that are intended to protect drinking water supplies from pollution and runoff — a move that will benefit his golf courses.

It is clear what Mr. Trump needs to do: sell his businesses and put the proceeds in a blind trust overseen by independent managers. But he has refused and says he has addressed the problem by handing control of his companies to his sons. That arrangement is a sham. He still owns his businesses and his family is hardly independent of him.

Regrettably, the Republicans who control Congress have decided they have no obligation to hold presidents of their own party accountable. Despite repeated requests by Democrats, they have shown little interest in investigating Mr. Trump’s business interests when there are compelling reasons to do so. Just this week, The New Yorker reported that Mr. Trump licensed his name to a hotel and residential tower being developed by a political family in Azerbaijan that has close ties to an Iranian group linked to that country’s elite Islamic Revolutionary Guards Corps.