Trump’s continued insistence he will build a border wall and make Mexico pay for it has one purpose…
He is pandering to his base to keep the base happy. Take the following, for example:
“President Trump’s campaign has been targeting supporters with Facebook ads, vowing to build the wall on the southern border, despite “rumors” to the contrary. (In fact, those ‘rumors’ come from a statement put out by Sen. Chuck Schumer and Rep. Nancy Pelosi, reporting they had reached a border security deal with Trump that did not include a wall.) These ads don’t appear as regular News Feed posts on Trump’s page. Instead, they’re only visible to the Facebook users his campaign targeted.
Pandering to the base is a tradition as old as politics itself. But in the social media age, it’s easier than ever for politicians to take those tailored messages—the kind they might not like to share with the whole world—and disseminate them only to the people who are most likely to agree. And targeting allows campaigns to silo thousands of possible audiences with just a click, making it harder than ever to hold politicians accountable for all of it.” Wired
This type of campaign allows Trump to deliver different messages to different targeted groups, and he can get away with it. This is not a Trump thing, it is a normal political thing.
Welcome to the age of digital political advertising.