(JNS) — Last Tuesday, two notable events occurred in the Democratic Party. Joe Biden announced that he had selected California Senator Kamala Harris to serve as his running mate in November; and Rep. Ilhan Omar won her primary, all but guaranteeing her return to Congress for a second term.

On the face of things, Harris’s selection seems like the more significant of the two events. But actually, Omar’s primary victory was far more momentous.

Traditionally, presidential candidates have selected their running mates based on electoral considerations. For instance, in 2016, then-Indiana governor Mi...