Donald Trump is exposing how much of the presidency relies purely on tradition

President-elect Donald Trump has not released his tax returns. He has not given a formal press conference since his election. He wants his private security team to supplement the Secret Service. He is skipping many intelligence briefings because he is, "like, a smart person." And none of those things — along with many of the incoming president's other unconventional choices — are against the law.

As Politico explains in a new analysis Friday, Trump's decision to flout tradition at every turn "is shining a light on how much of the American political system is encoded in custom," not law. Much of what we expect the president to do and say is not grounded in any requirement more formal than longstanding practice — and that suits Trump just fine. "If it's not written down, you can get away with it," says Trump biographer Gwenda Blair. "That's the new premise."

The question once Trump takes office is how much he will push boundaries with real legal heft. As a candidate, Trump "said things that were clearly unconstitutional, but there's no legal prohibition about saying you're going to do something unconstitutional," explains Richard Painter, formerly chief White House ethics lawyer under President George W. Bush. But there is a legal prohibition "against doing something unconstitutional," and Trump will have to learn the difference if he wants to avoid offering grounds for impeachment to critics ready to pounce.