With all the recent attention on Rachel Bitcofer’s model we have not really looked at it what it may mean.
I don’t expect that the specific nominee the Democratic electorate chooses will matter all that much unless it ends up being a disruptor like Bernie Sanders.
Trump is not important to the general base assumptions of the model, merely an accelerant to underlying trend. Basically the model measures the hyper-partisan sorting of the electorate into a strictly binary choice. Elections are to be understood not with crossover but with activation of the particular tribe. Given the underlying demographics the Clan that activates their members win in the available districts. Under this case it is the marginally attached members who are important. Do they choose to vote or not?
Policy basically means nothing as whatever is stated will be interpreted as white or black by the tribe. It is the emotional attachment of the members that is important.
It is assumed here in the bubble we live under that a progressive approach thus is a winning one. It would after all appear to have the most emotional appeal to our base. But does it? That is the core question of the coming election.
Bitecofer has acknowledged she underestimated the Red reflection turnout effect. That played out more in the Senate then the House. In effect Trump’s fear of invasion and liberals' worked in mitigating the expected. Her current projection of the electoral map is basically Clinton 2016 without complacency. Trump all on his own has wiped that out.
The Case for a Moderate at the top of the ticket therefore becomes very straightforward. In the zero sum game of turnout the less scary alternative will depress Republican marginally attached and reassure Democratic marginally attached voters. This is with the understanding that the Democratic base is a bit more moderate then we here like to think. I would also add this is less to do with the Presidential race (except the college margin) then it is the down ballot races we need to pass anything of substance.
Looking at the Bitecofer model projections of swing states we have to consider if a progressive exciting the base will gain us more then a moderate reassuring. In particular can it excite the tribe enough more then Trump already has, the a backlash reflection would, and in places we need down ballot.