Joe Biden on Tuesday had a message for migrants considering crossing into the United States: 'Don't come over.' The president's team is struggling to cope with a surge of migrants at the U.S.-Mexico border, in what is shaping up, along with the fight against COVID, to be one of the biggest challenges of his first 100 days. His Homeland Security Secretary, Alejandro Mayorkas, said on Tuesday that the country was on track to see the highest number of arrivals across the southern border in 20 years. Yet the White House still refuses to describe the situation as a crisis.