I generally agree with Raikoulover on the simple game theory mechanics of it... but I do think we have to consider nuance, background, and that it does matter HOW protest is done, HOW pressure from the left is applied. Again, personalities.
We've already touched on it, but I do think comparing the situation Bill Clinton found himself in to what Kamala Harris finds herself in is the most illustrative of how the same lesser evil mechanics might not always play out the same way.
For Bill Clinton, you had opposition that was nearly identical to what he wanted to become politically (Reagan's dems also being neoliberals), and a set of mega donors that would be essentially identical with either party. You had traditional populism already waning compared to hot middle class interests, and a voter base that agreed with Reagan's party's economic project and wanted to see American enterprise run hot. If he lost, the consequence to him and the Democrats would be comparatively much less, letting the Republicans win again far more problematic for the unions/left than for the party.
In terms of ability to negotiate a dominant position against the left, Clinton had the strongest hand. "Where elst are y'all gonna go?"
For Kamala, the other side are literally perceived as a fascist end to Democracy. There are definitely those in the party and donors who have shown there ass, that they don't believe it or were too complacent to care enough to fight over Biden about it. But without question even the change in the ticket was forced through in part because significant faction of the Party Leadership AND it's wealthiest donors AND its media/upper class voter blocks genuinely, genuinely believe that the Republicans are fascists and a Republican win is unacceptable. Furthermore, she is coming in with a huge upsurge of enthusiasm, but also on the back of the frailest posture in tems of democratic legitimacy and party legitimacy. She is not given a mandate, she's forming it-- but a critical part of that mandate is that she's useless to EVERYONE (donors, party leadership, voters, her own legacy and career) if she loses. For everything she truly cares about, She MUST win.
Therefore, when it comes to negotiating with the left/the base/the protestors, Kamala's position is far, far weaker.
And the donors have a weaker oppositional position to the left as well, because a major set of them want to win EXCLUSIVELY WITH THE DEMOCRATS. Because they also have division amongst themselves, because despite being massively pro-Israel, many of them are also humanitarian filanthropists, and shit like what happened to the World Central Kitchen workers and similar orgs that ultimately work for them was unacceptable. And on top of all that, you have America's global allies, who all side with urgency towards resolution in the eyes of international law. The Democrats still do desperately want to be the party that lives up to legitimacy in leading a global order for and with its allies.
And finally, yes it does matter how protests happen. The left has been training, and grinding, and improving itself, and also inbedding itself. The Uncommitted Movement is not a Ralf Nader style outsider play, it is a very disciplined Bernie Sanders style insider play. You run INSIDE the party, you maintain discipline as a strong critique that's not disloyal to the Democrats, but applying immense framework within the party's framework. Ie. you go on MSNBC and to the ballot box with disciplined, strong, clear, and good faith demands. This DOES make those demands that much more potent, and that much more difficult for Kamala/Democrats to ignore at a human level. (which again, matters)
All of this is to say, that lesser of 2 evils voting is a disgustingly critical framework baked into our first-pass-the-post system, but that the context definitely matters, and will shape how that dynamic plays out.
The left should recognize that Kamala CANNOT run the Bill Clinton playbook, she IS too weak to do that, and protesters ARE RIGHT to push through demands now and continue to pressure Kamala/Walz in the future. That said, don't step on the neck, don't burn down the house-- we need to win together, so we need her to have an avenue to save face.
We know we're in a much stronger negotiating position; it's time for the wider movement to maintain disciplined resistance while we let good leaders make the case to the ticket behind the scenes, which will likely fall on far more empathetic ears that other recent Democratic leaders'.