The first of the great missions that the president of the United States, Joe Biden, entrusted to his vice president, Kamala Harris, is what Politico defined as “a political grenade ”: to confront the root causes of immigration that are leading to the greatest number of people from Central America in decades, and unprecedented in the case of minors, to cross the southern border without papers. The politically radioactive potentialThat charge has been demonstrated from the outset, with Republicans indulging in incessant criticism of Harris, even though his role does not cover all immigration or, specifically, actions on the border.…