It’s great that President Trump, while having failed to curb illegal immigration, and while still struggling to build his “wall,” is engaged in piecemeal efforts to stop the flow of migrants bum-rushing the southern border. His supporters undoubtedly appreciate it, but they should know: Once Trump is gone, everything he tried to do will disappear with him.

Trump is heralding a “deal” he got with Mexico — he even waived a little piece of paper at the White House on Tuesday as proof! — that’s supposed to block off the hundreds of thousands of Guatemalans, Salvadorans, and Hondurans from trekking up to the United States, where they’re securing legal protection to stay just by claiming asylum.