1. The Candidates on Climate Change Joe Biden Pete Buttigieg Kamala Harris Beto O’Rourke Bernie Sanders 2. The Candidates on Gun Violence Joe Biden Cory Booker Pete Buttigieg Kamala Harris Amy Klobuchar Beto O’Rourke Bernie Sanders Elizabeth Warren 3. The Candidates on Healthcare Joe Biden Cory Booker Pete Buttigieg Tulsi Gabbard Kirsten Gillibrand Kamala Harris Amy Klobuchar Beto O’Rourke Bernie Sanders Elizabeth Warren 4. The Candidates on Immigration Joe Biden Cory Booker Pete Buttigieg Beto O’Rourke Kirsten Gillibrand Kamala Harris Amy Klobuchar Bernie Sanders