In a contentious Oval Office meeting, President Donald Trump and the Democratic congressional leaders — Nancy Pelosi and Chuck Schumer — disagreed over funding for a border wall, mangling some facts in the process. The president claimed that “a lot of the wall is built,” and he cited statistics purporting to show “it’s very effective” at stopping illegal immigration. But his figures correspond to those in a Customs and Border Protection video on various border security strategies deployed before he took office, from 1992 to 2016. And in most sectors Trump cited as successful, there is very little fencing...