President Trump on Monday challenged House Speaker Nancy Pelosi, who has called the White House's proposed southern border wall "an immorality," to explain why she is not insisting on the removal of existing physical barriers, or opposing ongoing construction of new wall projects near San Diego, Calif. Trump, in a follow-up tweet, asserted that the country needs a "powerful Wall" to deter the incoming migrant caravan that marched freely through the Guatemala-Mexico border last Friday, after the gates were left wide open by officials seeking to avoid a confrontation. The caravan, which consists of approximately 1,000 Central American migrants, was...