EL PASO, Texas (AP) — Kamala Harris is facing perhaps the most politically challenging moment of her vice presidency when she visits the U.S.-Mexico border Friday as part of her role leading the Biden administration’s response to a steep increase in migration. While in El Paso, Texas, she will tour a Customs and Border Patrol processing center, hold a conversation with advocates from faith-based organizations as well as shelter and legal service providers, and deliver remarks. The vice president has faced months of criticism from members of both parties for declining to make the trip thus far and for her muddied explanations as to why.