Impeachment hangs on whether Trump's actions were illegal or merely ugly

In the first 175 years of the Republic, the House of Representatives impeached only one president, Andrew Johnson. Now, in the last 57 years, we have impeached two presidents, Richard Nixon and Bill Clinton, and are on the verge of impeaching a third. It’s worth considering the modern rise in impeachments: Are presidents really that much worse, or is something larger afoot?

We normally evaluate a president’s performance through elections. We are continuously shown opinion polls about what people think of President Trump and impeachment, but impeachment is not a popularity contest. The people’s view properly comes to the fore a year from now in the 2020 election.