(CNN) – Sen. Blanche Lincoln had an early lead over Lt. Gov. Bill Halter in Arkansas' Democratic primary for U.S. Senate.
With 21 percent of precincts reporting, Lincoln had 44.8 percent of the vote. Halter had 41.1 percent, and fellow Democrat D.C. Morrison had 14.1 percent.
A runoff will be held if no candidate gets more than 50 percent on Tuesday.
Lincoln, who is seeking a third term, appeared to be in a tough primary campaign partly because some Democrats criticized her for not supporting a public health care option during the debate on health care in Congress.
Halter received the support of unions and progressive organizations.