Wasn't she the Attorney General - IOW, the "Top Cop" - of California? Even with her "racial qualifications" that's got to be a bit difficult for the most extreme BLM activists to stomach.
Interesting choice. Basically a kind of "screw you!" to the AOC/"progressive" wing of the Democrats.
It does kind of make you wonder whether some of the back-room string-pullers in the party think they're going to lose this one anyway, so they're trying to position themselves to have a better shot for 2024.
Most of us here on the board lean conservative/Republican, so we don't necessarily see the internal struggles of the Democrats, but there has been a very real and very nasty fight going on for years between the "pragmatic" wing of the Democrats (Hillary being the best example) and the "progressives", radical leftists of the AOC/Bernie Sanders variety.
The thing is, the "pragmatics" NEED the anger and intensity (and most importantly the NUMBERS) of the "progressives" to win, and the "progressives" need the money and mainstream support that comes from the "pragmatics" (because for some weird reason, wealthy business owners aren't huge fans of the "kill the wealthy and take all their money" radicals on the "progressive" side. Go figure.

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Since neither side is big enough to take over the whole party, and since the margins for getting elected are so razor thin, each wing of the party effectively holds a gun to the head of the other wing - a kind of "mutual assured destruction" is what results. IOW neither side can win by itself, but simply by staying home, they can make the party lose, denying the other wing the power it wants.
Each wing seems to believe if they just hang on, sooner or later they will hold enough of a majority to force the other side out of the party without costing them the election.