What did Donald Trump do today?

He spoke on the phone with the President of Taiwan, in the process causing both diplomatic and ethical problems.

The United States has only informal relations with Taiwan, which the People's Republic of China regards as a renegade province. The diplomatic situation is complicated, but Trump openly treating the Taiwanese President as a fellow head of state would be roughly equivalent in diplomatic terms to China referring to Hillary Clinton as the "Popular Vote President of the United States." It does not seem likely that Trump understood the significance of his actions, although the Taiwanese government certainly would have.

The fact that the Trump Organization is looking to build in Taiwan--and will therefore need the cooperation of the Taiwanese government--makes this one of several calls where Trump's business goals and foreign policy may be getting mixed up.

Why should I care about this?

• It's extremely bad if foreign policy is being affected by a president's financial interests.

• It's only a little less bad if it just looks like foreign policy is being affected by a president's financial interests.

• A president who doesn't know or care about diplomacy is likely to have it used against him by countries that do.