So long as she controls California, Harris can make life very difficult for any prospective challengers seeking volunteers, operatives and dollars. If, as seems likely, Democrats demote the Iowa caucuses and give Nevada the first presidential nominating contest, having a political infrastructure in neighboring California will only become more, not less, valuable.

The Democratic bench, already so desperately thin that Mayor Milquetoast is viewed as a plausible standard-bearer, looks even thinner when one turns southward. To put the matter bluntly, even if they do not love her, who could win Southern black voters away from Kamala Harris in a Democratic primary? Warren? No. Klobuchar? C’mon. Buttigieg? No way. Mitch Landrieu will enjoy fawning Morning Joe coverage, but it will make no difference to the eventual implausibility of his candidacy.

Finally, Biden’s own political incentives help Harris. Even if Joe decides tomorrow to forego reelection, he’ll keep the decision a secret for as long as possible. Making himself a lame duck any earlier than necessary would bury his effectiveness in office. As a result, Biden will freeze the field by giving every indication of running for reelection even if he has no intention of following through on the threat. No other Democrat can ramp up a large political apparatus without appearing to be challenging Biden as the incumbent.