A kidnapper demands ransom, and his threat to kill the abducted child is credible. Assuming the child’s parents have the means to pay the ransom, is there any reason they would not yield? The only reason I can think of might be the hope that law enforcement can capture and disarm the kidnapper before he can carry out his threat.
Kidnapping of course is a form of hostage taking (which in turn is a form of blackmail). We are witnessing a hostage taking situation right now in the United States. The hostage(s) are 800,00 federal employees and the populations they serve. The threat is not to kill them but to prolong their suffering. The hostage taker is the president of the United States. In contrast to the kidnapper, this hostage taker is immune to capture by law enforcement. But like the kidnapper, this hostage taker is fundamentally amoral—a sociopath who simply doesn’t care about the hardships he causes others. All he cares about is his ransom—in this case, not money but the supreme satisfaction of winning. Winning, for Trump, is an imperative next to which all other values pale.
Therein lies his advantage in his confrontation with the Pelosi/Schumer Democrats: being more or less normally socialized adults with more or less normal consciences, they do care. Which is why they are more likely eventually to yield. I don’t see Trump ever yielding. There is no way enough Republicans in Congress will ever cross him to over-ride a presidential veto, so why should he give up? He has made the wall the defining objective of his presidency, and he must win. His base expects it.
Trump, of course, blames the Democrats for the shutdown. That’s like the kidnapper blaming the parents if they refuse to pay and he murders their child. But they surely would pay if they knew there were no chance of apprehending the kidnapper in time.
The Democrats, after a further show of resistance, should offer Trump a face-saving way out—some funding for something he can call a wall, balanced by DACA relief. (Something like what they offered him a year ago, but not as good for him.) Trump knows that the shutdown is hurting him politically, so he might accept such an offer, calling it a win. But he might not. (Ann and Rush might say no.) Alternatively, he might declare a state of emergency, diverting funds appropriated for other purposes to build his wall. Since there actually is no emergency, such an act would constitute a gross abuse of power. It would be an impeachable offense, but it might well be the most likely way this sordid affair will come to an end.