Immigration; Rep. Pelosi; Lisa Randall

Law professor Nancy Morawetz and journalists Evan Osnos, Bob Costa, Michael Crowley, Mark Halperin, and Michael Heilemann discuss the constitutional and political implications of Trump's vow to bar Muslims from entering the U.S. Minority Leader of the U.S. House of Representatives Nancy Pelosi joins guest host Al Hunt to discuss the status of the spending bill, the plight of the Syrian refugees, and the issue of gun control. Theoretical physicist Lisa Randall explains the nature of dark matter and introduces her book “Dark Matter and the Dinosaurs,” which looks at the role of dark matter in the evolution of the universe, our solar system, and life on Earth.