United States general election

Democratic presidential candidate former Vice President Joe Biden speaks during a community event, Wednesday, Oct. 16, 2019, in Davenport, Iowa. (AP Photo/Charlie Neibergall)

Democratic presidential candidate Sen. Bernie Sanders, I-Vt., left, former Vice President Joe Biden and Sen. Elizabeth Warren, D-Mass., right, participate in a Democratic presidential primary debate hosted by CNN/New York Times at Otterbein University, Tuesday, Oct. 15, 2019, in Westerville, Ohio. (AP Photo/John Minchillo)

Democratic presidential candidate Sen. Bernie Sanders, I-Vt., left, former Vice President Joe Biden, center, and Sen. Elizabeth Warren, D-Mass., raise their hands to speak during a Democratic presidential primary debate hosted by CNN/New York Times at Otterbein University, Tuesday, Oct. 15, 2019, in Westerville, Ohio. (AP Photo/John Minchillo)

Democratic presidential candidate Sen. Bernie Sanders, I-Vt., speaks during a Democratic presidential primary debate hosted by CNN/New York Times at Otterbein University, Tuesday, Oct. 15, 2019, in Westerville, Ohio. (AP Photo/John Minchillo)

Democratic presidential candidate Sen. Kamala Harris, D-Calif., left, and Sen. Bernie Sanders, I-Vt., gesture to each other during a Democratic presidential primary debate hosted by CNN/New York Times at Otterbein University, Tuesday, Oct. 15, 2019, in Westerville, Ohio. (AP Photo/John Minchillo)

Donald Trump, Jr. speaks to supporters of his father, President Donald Trump, during a panel discussion, Tuesday, Oct. 15, 2019, in San Antonio. (AP Photo/Eric Gay)

Vice President Mike Pence listens as Treasury Secretary Steven Mnuchin, speaks to reporters outside the West Wing of the White House, Monday, Oct. 14, 2019, in Washington. The U.S. is calling for an immediate ceasefire in Turkey's strikes against Kurds in Syria, and is sending Pence to lead mediation effort (AP Photo/Jacquelyn Martin)

Student athletes pass a CNN sign on an athletic field outside the Clements Recreation Center where the CNN/New York Times will host the Democratic presidential primary debate at Otterbein University, Monday, Oct. 14, 2019, in Westerville, Ohio. (AP Photo/John Minchillo)

In this Oct. 4, 2019 photo, Marty Small speaks at a swearing-in ceremony in Atlantic City, N.J. that installed him as acting mayor following the resignation of Mayor Frank Gilliam Jr.who admitted stealing $87,000 from a youth basketball team. On Tuesday Oct. 15, 2019, the City Council is expected to choose Small to be mayor until the Nov. 2020 general election. Listening is his daughter Jada, left. (AP Photo/Wayne Parry)

Democratic presidential candidates chosen to participate in fourth debate;