WASHINGTON (AP) — President Joe Biden has tapped Vice President Kamala Harris to lead the White House effort to tackle the migration challenge at the U.S. southern border. She also is tasked with working with Central American nations to address root causes of the problem. Biden, in delegating the matter to Harris, is seeking to replicate a dynamic that played out when he served as President Barack Obama’s vice president. Obama turned to Biden early in his first term to lead the White House effort to draw down U.S. troops in the intractable war in Iraq. With the move, Biden hopes to show he’s taking the situation at the U.S.-Mexico border seriously.