Each of these individuals is a loss to the political resistance.

There have been some of these, but I don't think its that large of a population. I see a whole lot more people becoming part of the solution than anything else. Maybe I am wrong on the population distribution, but I just don't see what your saying happening on a scale large enough to cause an end to the movement.

If there's a plan to save America the clock is ticking, momentum could quickly die on the vine without visible meaningful victories

But there are so many visible victories. How meaningful they are is up to the individual, and some lose hope because they want even bigger victories, but the vast majority gain resolve and purpose from all the victories we do have. Maybe I'm delusional, but that's what I see. Momentum seems to be on the upswing. This is the wrong time to be worrying about a mass exodus imo.