Will Democrats ever say yes to immigration reform? They now have an opportunity to do so as President Trump demands funding for additional miles of physical barrier along the southern border.

But rather than providing Mr. Trump money in return for immigration changes they say they want, congressional Democratic leaders are rebuffing the request with focus-group-tested rhetoric: House Speaker Nancy Pelosi called a border wall “immoral, ineffective, expensive.” Presumably having seen the same data, Senate Minority Leader Chuck...