listen.
it's not a question of what side people take on the wall issue. as mentioned, i actually don't care if they build a wall or not. and, this isn't something that affects 95% of people directly, so that is going to be the broad response.
i've pointed out a bunch of times that i have a math degree, but i've never worked on the data side of a survey firm. i did, however, work as a survey interviewer for many years as i was going through school; my direct experience is not crunching umbers, but asking people questions. and, i know how this works better than most - you have to get somebody to answer a complicated thing with a binary response, and you get all this skewed data as a response to it.
consider the following question: would you prefer stalin or hitler?
and, the person is going to hum and haw and say they don't like either, but my responsibility as an interviewer is to get them to answer the damned question: stalin or hitler. pick. damn it.
and, if we learn that 60% of people prefer stalin to hitler, does that mean that 60% of people support stalin? remember: he's dead. he can't hurt you.
trump may not win this argument directly, but i never said that he would. so, you can do all of this polling and come up with these awful results and deduce he's losing - then end up baffled when he wins re-election with a 30% approval rating, because the democrats are running at 25%. and, this is the danger the democrats are running up against with this: you don't have to actively support the wall to get pissed off that the government is shut down. you don't have to be pro-trump to turn on the democrats for being obstructionist. you don't even have to oppose illegal immigration to get frustrated by not being able to go camping.
the error the democrats are making is in thinking that they're going to be able to deflect this all to trump. they won't - they're going to have to eat a substantial percentage of this. the last time that nancy pelosi was in charge of congress it had a 9% approval rating at it's lowest point, i believe, which makes trump look popular in comparison.
so, i will state what i said previously. the obvious kneejerk is to blame trump, and i don't know how long that holds for. but, the democrats are the one playing a dangerous game here, not trump - the longer this goes on for, the more they risk a backlash. that backlash may not translate to republican support, so much as it manifests itself in apathy towards the democrats, which is probably their bigger threat amongst certain demographics. but, they can't win this, in the long run - they can just turn voters against them.
if it was something more substantive, it could be different. but, nobody wants to suffer to avoid building a wall that doesn't affect them in any way at all. and, people are eventually just going to be looking for the easiest way to get paid - as they find themselves abandoned by a democratic party that is either more interested in questionable abstract symbolism than economic facts, or in undocumented workers than unionized labour.