Trump didn't cave, he played it well.
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Trump got the Dems to agree to form a committee to establish what is necessary to protect the border and on that committee will be qualified people that will insist the wall is necessary. So, now if the Dems do not follow the expert’s advice their true motive of not really wanting to protect the border will be exposed and Trump will be justified to use emergency measures.
In the meantime, Trump has shown that he is humble enough to bend to the Dems stubbornness of not negotiating with the shutdown in progress, he’s gotten the workers paid and showed that he cares with that gesture, he let Dems look childish for canceling the SOTU and did so without backlash and whether or not the Dems agree to the funding after 3 weeks Trump will get his wall in the end like he said he would despite their every effort to obstruct.
Again, nice spin!