See, that's what I meant with the Democrats are playing his game. Trump is not personally interested in whether or not a wall is built. He made this promise, and the Democrats are preventing him from doing so. Politically, that is the best thing that could possibly happen to him. He won't have to build a wall, and he won't have to prove that it's not useless. He can say the Democrats are unwilling to negotiate with him, which is even true. People will get used to the shutdown as a new normal situation quite easily. I bet a lot are happy that the IRS won't be working. And all the (mostly poor) people who will suffer from the shutdown? Trump can easily blame the Democrats for that. A lot of people will be put off by the Democrats through Trump's scapegoating, and Trump will win in a landslide in 2020. And all this is not even taking into account that Trump has made uncanny references to national emergency lately.
I'm having a hard time with this line of thinking. What are Democrats supposed to do? Give him the 5 billion? A bipartisan budget was already approved by both chambers before Trump walked back on it after being blasted by right wing media. He then went on TV and said he would own the shutdown. Democrats are negotiating, but there's no reason to offer Trump anything at this point. The wall isn't popular. Once airports start to shut down due to a lack of TSA agents, there is going to be a ton of pressure on Trump to cave. If Democrats give into Trump, Pelosi will lose all credibility with the left. They can't afford to give him what he wants especially now when he is on the defensive.
I'm still not sure that declaring a state of emergency is a bluff or not. Trump has backed himself into a corner though and is going to have to do it. I don't see Democrats caving on this one and they shouldn't. I'm not really sure what happens next. The wall debate is really more of a messaging war than anything else. It won't actually be built no matter what happens. It will spend years working its way through the courts before being canceled by the next Democratic president, whether it is built through executive action or approved by congress. Democrats know this, Republicans know this, even Trump knows this. Democrats are trying to frame this as a matter of keeping the government open vs wasting billions on a wall that nobody outside of Trump's base really wants. So far, opinion polls show that this is working so far.
As for electoral consequences, there won't be any for anybody. The election is a little less than two years away. Assuming this shutdown doesn't extend into the summer or later (it won't), it won't be on anybody's mind come election day. The election map is also not really set up in a way that would allow anyone to have a landslide. That being said, the border wall was his marquee campaign promise and he has to deliver on that if he wants to win. The blowback he got for indicating he'd sign the budget back in December is proof that his supporters will turn on him over this. Even the more traditional conservatives who currently support him but do not like the wall would see Trump backing down as a sign that the dealmaking abilities he sold himself on during the campaign.
To that end, I think there's a bit of hyperbole around Trump, particularly outside the US. Trump won by a razor-thin margin and has shown very few signs of growing any coalition for re-election. He might go into 2020 with a more unified GOP, but his path to victory is going to be very similar to 2016. It's really not looking good for him. He can definitely win again, but it is far from a foregone conclusion and it will be another very narrow victory. He is not popular here and while he has major media voices firmly on his side, they will just as quickly drop him when it is convenient to do so.
One aspect of this that isn't being discussed as much is the squandering of a perfect opportunity to strip some power away from the executive. Conservatives complained throughout the Obama presidency that the president has too much power, particularly when it comes to immigration. This is actually something I agree with conservatives on. By passing a veto-proof budget 100 - 0 (the votes are certainly there), McConnell would be making a pretty big step toward bringing some power and authority back to congress. By refusing to hold a vote to shield Trump from having to veto, he is essentially allowing the executive to hold congress hostage. Of course, McConnell is up for re-election in 2020. By not caving in to Trump, he would open himself to a primary challenge. Personally, I think Republicans would be making a colossal mistake by ditching McConnell but that is what happens when you let fringe groups take over the party.