Set aside the fact that Rex Tillerson, the chief executive of Exxon Mobil and Donald Trump’s choice for secretary of state, knows scores of world leaders and is a skilled businessman. Why would Mr. Trump choose as his top diplomat a man whose every decision or action would be tainted by suspicion that he’s capitulating to Russian interests or those of the oil industry, having spent his entire career at Exxon Mobil?

Mr. Trump seems impervious to ethical standards. By naming Mr. Tillerson, he risks burdening his administration with another appointee likely to ensure endless controversy.

Mr. Tillerson has no background in diplomacy beyond corporate deal making. And his relationship with Vladimir Putin, Russia’s authoritarian leader, raises serious questions about whether he could manage Russia policy in a way that advances America’s national interests. Mr. Putin even gave him an “Order of Friendship” award in 2013.

American-Russian relations are at their worst since the Cold War, a result of Mr. Putin’s annexation of Crimea, the war in eastern Ukraine, his attempts to destabilize countries in Europe, and bombings of civilians in Syria. The Central Intelligence Agency’s newly revealed judgment that Russia interfered in the election to hurt Hillary Clinton adds a frightening dimension to the relationship.