Why the president becomes more powerful when Congress fails

I'm going to be a bad pundit for a second and confess uncertainty: I don't know what I think of President Obama's rumored executive action to lift the deportation threat against millions of unauthorized immigrants. It could be a perfectly sensible policy or a worryingly undemocratic one. But since there are literally no public details about what it is or even whether it will happen it's hard to make a call. (On a related note, I also don't know what I think of the iPhone 9.)

That said, I want...