Henry Olsen argues at National Review Online that proposals to change the Democratic Party’s presidential selection rules could benefit a particular California senator.

Supporters of Bernie Sanders’s 2016 presidential bid have long blamed the Democratic party’s superdelegate system for his defeat. It’s no surprise, therefore, that they are pushing to reform that system, reducing or perhaps even eliminating slots for unelected and unpledged delegates. Recent reports suggest that they may succeed in doing so, but that their efforts will not help Sanders win the party’s nomination in 2020. Instead, they will make it likelier that another progressive will triumph: California senator Kamala Harris.

Harris, not Sanders, will be the probable beneficiary of the rules change because of the demographic makeup of the Democratic primary electorate. It would not be an oversimplification to say that the Democrats divide into three rough groups: progressives, centrists, and non-whites. African-Americans are by far the largest share of the last group, totaling nearly a quarter of all Democratic voters nationwide.

Democratic party nomination fights have followed a similar pattern since at least 1984. A candidate appealing to educated, more liberal Democrats challenges a relatively more centrist rival favored by the party establishment; the progressive wins most primaries and caucuses in New England, the West, and Wisconsin, while the centrist wins most of the remaining states. This outcome has historically doomed the progressive, from 1984 challenger Senator Gary Hart to Sanders himself, because there are more centrists than progressives or liberals.

The non-white vote, and especially the African-American vote, plays an underappreciated role in this process. Non-whites almost invariably back the more centrist candidate, providing that person with key support to defeat his or her more liberal challenger. …

… African-American voters do break from this mold, however, when a serious African-American candidate is running.