Teachers like this exist. One of my kids had an elementary school teacher like this. Two examples:

1. The math assignment was about currency denominations; what coins and bills you need to make up $7.42, for example. My kid answered using $2 bills (uncommon in the US but still printed), as we have them at home. Teacher marked the answer wrong because teacher didn’t mention $2 bills in class.
2. The writing assignment was to rewrite the Snow White story from the perspective of another character. My kid, having read a bunch of those “twisted tales” and recently fallen in love with “Wicked”, wrote from the evil queen’s perspective and made her a sympathetic character. Teacher marked her down for “changing the story” without acknowledging my kid’s creativity. Teacher did not back down when we confronted her on this during our parent teacher conference.

(FWIW, in both cases we reassured our kid that they did great in both cases, and that we were proud of them.)

HE STEALS ONLY WHAT HE CAN’T AFFORD… THAT’S EVERYTHING!

Let me restate your point to make sure I understand it, as I haven’t seen your point expressed elsewhere.

Scenario 1:

• Democratic candidate for president is Biden.
• Progressives want a more progressive candidate for the next election, so they refuse to vote for Biden.
• As a result, Trump wins the election.
• In the 2028 DNC primaries, the democratic candidate for president is more progressive than Biden was.
• Progressives vote for the dem candidate, who wins.
• The democratic party is permanently shifted leftwards.

In this scenario, having a more progressive president in 2028 (and beyond) outweighs the damage caused by a Trump presidency.

Scenario 2:

• Democratic candidate for president is Biden.
• Progressives decide to vote for Biden, despite their distaste.
• As a result, Biden wins reelection.
• In the 2028 DNC primaries, the democratic candidate for president is similar to Biden.
• The democratic party stays centrist, to the distaste of progressives.

In this scenario, avoiding a Trump presidency is worth giving up the opportunity to move the democratic party permanently more leftwards.

Do I have this right? If not, please, I’m truly curious, as I find your game theory points compelling.

Assuming I do have your position correct, I think you’re making a couple of inaccurate assumptions:

• While the DNC clearly tips the scales in favor of its preferred candidate, the DNC is not the sole decision maker. (For example, in the 2008 primaries, the voters chose Obama despite the clear preference of the DNC for Clinton.)
• A Trump presidency would be singularly bad for the nation, both in the short term (e.g., immediate repeal of executive actions on gun control, clean energy, and LGBTQ+ rights; increased support of Israel’s genocide in Gaza) and long term (e.g., more MAGA judges and justices, further emboldening the GOP to be more MAGA). It’s also possible that a Trump presidency effectively ends proper democracy in the US, meaning any potential gains of a future progressive president would be irrelevant.

I agree that the more we push the party leftward, the better for all. But I believe the time to do this is in presidential primaries, state/county/local elections, local and national organizing, and even personal outreach to individuals (admittedly, this last one is very small scale, but it’s also the only way to truly change people’s minds and positions).

No matter how much you think both candidates are shit, you must be able to realize that one is far and beyond worse than the other.