The relationship between support for the president and the wall is so tight that it’s hard not to wonder whether, at least for now, support for the wall is simply a function of support for the president. In other words, attitudes about President Trump might drive attitudes about the wall, rather than the other way around. It wouldn’t be much of a surprise, given how strongly voters feel about the president and the extent that he’s emphasized the issue.

It’s hard to see how the issue can be used to help him win re-election. Midterm exit poll data, election results, voter file data and pre-election polls indicate that the president’s approval rating is below 50 percent in states worth at least 317 electoral votes (270 are needed to win).

That’s actually a relatively healthy number for the president compared with his national approval rating (around 41 percent), but it could be a conservative estimate, and voters’ views might be unusually entrenched, given the stability of his ratings.