Former vice president Joe Biden, the frontrunner for the 2020 Democratic presidential nomination, called on Monday for reinstating a ban on assault weapons and including a buyback program to get them off the streets. In a column in The New York Times, Biden also called for stricter background checks for gun buyers and greater use of “smart-gun technology” that allows a weapon only to be fired by its authorized owner. “We have a huge problem with guns,” Biden said in the article published about a week after mass shootings in El Paso, Texas, and Dayton, Ohio, left 31 people dead.