Charles M. Blow: Biden Becomes a Boon for Democrats

The coattail effect in politics is the theory that the popularity of a candidate at the top of the ticket redounds to the benefit of those in the same party down ballot. You vote Democratic for president, then you might vote Democratic for senator or mayor. But what do we call it when the person from whom the benefit flows is not actually on the ballot? What if the person isn’t even personally that popular?