Senators and presidential campaigns

Six senators currently contending for the Democratic nomination for president. Left to right: Bernie Sanders, Kamala Harris, Elizabeth Warren, Cory Booker, Amy Klobuchar, Michael Bennet. (From public domain images.)

A sitting senator has never defeated an incumbent president.

This, in and of itself, is not a particularly remarkable fact, given that there have only been five cases in which a sitting senator challenged an incumbent president, and in one of those cases, the senator resigned from office before the election. However, it does reflect two persistent and statistically significant facts of American…