PRESIDENTIAL PREFERENCE VOTE (D): Biden, Phillips, Williamson, uncommitted. 40 delegates at stake. All voting conducted by mail between Jan. 12 and March 5.

WHO CAN VOTE: Registered Democrats only

NOTES: Iowa Democrats moved away from their traditional caucus system this year after party rules rearranged the calendar and barred the state from holding a presidential nominating event in January. Democrats in the state still held caucuses to conduct party business that month, but its presidential nominating contest became a preference vote conducted by mail with results released on Super Tuesday.