President Trump claimed in a series of tweets that he would declare a "national emergency" over migrant caravans moving toward the United States through Central America and Mexico. Here's what to know.

President Trump claimed in a series of tweets that he would declare a "national emergency" over migrant caravans moving toward the United States through Central America and Mexico. Here's what to know. https://t.co/t3k4vhnITi

— CNN (@CNN) October 23, 2018