As a hypothetical Democratic member of Congress
Trump halting funding to blue state projects only makes me dig in more. Trump never makes deals in good faith. He always tries to exert leverage without putting any real effort into trying meet people half way. The deal isn't real to him unless he forces you into submission.
If Democrats bend to Trump's slashing of blue state funds, he'll just do it again next time.
Budging to him will just show him that he can do whatever the fuck he wants... and he does that anyway. Some Democratic members budged to him last time, because they believed that shutdown would have given Trump more free reign, but that didn't work. Trump had a funded government that was supposedly constrained by appropriations law, and Trump still did whatever the fuck he wanted. The man still functionally wiped out an entire agency and gutted other, and still plans gut out more.
We have now learned the hard way that we have nothing to lose.