If either the Republican or Democratic rank-and-file panics, (the shutdown might end then)

If either the Republican or Democratic rank-and-file panics, it becomes very hard for the leadership to continue to hold out for their wish lists to end the shutdown.

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The polarization is similar to 1995 and 1996 right...

This is sort of the way this works. Though logically you would think it would be the middle Class and poor (the Democrats that would panic first) you also have to consider just how angry the Democrats are at Trump right now for destroying our country and institutions so much so far.

So, many are likely willing to demonstrate in the streets for months to make sure he is impeached as soon as possible.

Don't underestimate the anger of the Democrats right now against Trump. This is the one factor that Republicans just don't seem to understand. If Republicans don't get this there will be blood in the streets before this is over and neither party is going to benefit from that.