>The thing is, there's nothing to negotiate in terms of The Wall. It's yes or no.
Its been a bit more complex than that. The original funding bill was passed by both House and Senate back when they were under Republican control and Trump was all set to sign them until a media campaign by some high profile right wingers caught his attention. He's been moving the goalposts since then, pointing the finger at Pelosi and Schumer in the process (McConnell is missing in action). There is actually a significant amount of funding for border security in the funding bill, its not specifically for The Wall but there's enough to build, upgrade and repair significant sections of it. Trump has increased his demands and dug his heels in, "Proud to shut down the government" is the quote on TV. As for getting the Mexicans to pay for it, that's not going to happen unless you're a believer in contorted reasoning (however, as things stand it would need Mexican cement and Chinese steel -- problematical?)
The problem that Pelosi has is that if you cave into these unconstitutional demands its only a matter of time before you get the same tantrum -- its the kind of behavior you expect from toddlers, not adults.
Its also very similar to the problem that the UK has with Brexit. There's a very vocal group of politicians who want the UK to crash out of the EU on March 29th., something that will be good for Disaster Capitalists but probably not very good for ordinary people.