If the President actually decides to declare a national emergency in order to achieve public policy goals the Congress otherwise will not fund, then every single Democratic candidate needs to go on the record now with their plans to use the identical powers to fulfill their own policy objectives.
This is an absurd thing for Trump to do, but whining isn’t going to stop nor reverse it. Beyond fighting it in the courts, the costs to the Republican Party need to be made clear now. You support this, and we’ll use it to, among other things, regulate power plants, build wind and solar farms, and radically expand underfunded portions of the ACA. Just for starters.
Once this is done, it cannot be undone. So fine. We’ll fight it, and if we lose there, we’ll use it in a far more expansive manner than you can possibly imagine. Because there can no longer be any “these powers are for use by Republicans-only” bullshit anymore. Not if y’all insist on taking us down this path.