History isn’t a good guide for understanding Trump’s impeachment case
David Greenberg writes: The internet is awash in historical explainers and hot takes trying to make sense of our sudden constitutional crisis. Marshalled on behalf of a range of competing viewpoints, the arguments are sprinkled with references to Andrew Johnson, Richard Nixon and Bill Clinton—the three presidents who faced impeachment proceedings before Donald Trump. Which one applies to the current president and his apparent effort to enlist Ukraine in going after Joe Biden, his potential opponent in the 2020 election?…