E.J. Dionne: Why Trump gets away with everything

President Donald Trump greet visitors during a State Arrival Ceremony for Australian Prime Minister Scott Morrison on the South Lawn of the White House, Friday, Sept. 20, 2019, in Washington. (AP Photo/Patrick Semansky) A depressing mystery hangs over our politics: Why is it that when we have a president whose behavior puts our security interests in peril, our political parties can't confront the threat together?

Here we have a whistleblower from the intelligence community who, as The Washington Post reported, found a “promise” that President Trump made to a foreign leader “so alarming” that the “official who had worked at the White House went to the inspector general of the intelligence…