2020 Democrats prepare to debate in shadow of impeachment

Democratic presidential candidate and Mayor of South Bend, Ind., Pete Buttigieg speaks during a campaign stop at the Danceland Ballroom Saturday, Dec. 7, 2019, in Davenport. (Meg McLaughlin/The Dispatch - The Rock Island Argus via AP)

Democratic presidential candidate former Vice President Joe Biden, one of seven scheduled Democratic candidates participating in a public education forum, makes opening remarks, Saturday, Dec. 14, 2019, in Pittsburgh. Topics at the event planned for discussion ranged from student services and special education to education equity and justice issues. (AP Photo/Keith Srakocic)

Democratic presidential candidate Sen. Elizabeth Warren, D-Mass., speaks during a town hall meeting, Monday, Dec. 16, 2019, in Keokuk, Iowa. (AP Photo/Charlie Neibergall)

Democratic presidential candidate Sen. Bernie Sanders, I-Vt., speaks during a town hall meeting, Sunday, Dec. 15, 2019, in Keokuk, Iowa. (AP Photo/Charlie Neibergall)

LOS ANGELES — A winnowed field of Democratic presidential contenders takes the debate stage today for a sixth and final time in 2019, as candidates seek to convince anxious voters that they are the party’s best hope to deny President Donald Trump a second term next year.