What led Trump to change his mind? To go from an annoyed willingness to keep the government open (and avoid being blamed for the shutdown) to a refusal to do so unless more money for his border wall made it into the legislation?
Here's my working theory:
1. Trump watches and is influenced by a LOT of cable television (we know this from his Twitter feed, in which he quote tweets supportive cable voices)
2. Trump's go-to show is "Fox and Friends," the morning show on Fox News Channel -- his preferred cable TV network (we know this from his Twitter feed too)
3. On Wednesday morning, the hosts of "Fox and Friends" blasted Trump's seeming capitulation on the border wall.
"What a stunning turn of events," said Steve Doocy. "If [Trump] agrees to the [short-term funding resolution] which would continue funding the government at the current levels ... he loses and the Democrats will win everything they want."
Added Ainsley Earhardt: "People who voted for him and want the wall and went to the polls to vote for that wall, they want to know how he's going to do this and they want to know why he seems to be softening his stance this morning."
If you think that criticism didn't impact Trump's thinking on the wall, you don't know Trump. He prizes his political base over all else. And he views "Fox and Friends" as the in-house programming for the base. If "Fox and Friends" is blasting him, Trump knows his base hears it. And he doesn't like to ever get sidewise with his base. (In that, Trump is not totally unique. Most politicians always keep an ear to what their base is thinking and saying. But no president has done that to the extent Trump has.)