The heavy favorites in the Senate primary are former Gov. Roy Cooper, a moderate Democrat, and Michael Whatley, a former chairman of the Republican National Committee.

The race is one of a handful of competitive Senate elections this year, but Democrats seem most confident about North Carolina, partly because their candidate, former Gov. Roy Cooper, has never been beaten.

© Anna Rose Layden for The New York Times; Haiyun Jiang, via The New York Times

Democrats want to regain control of the chamber, and they have recruited some top candidates. But they are facing a tough map.

© Eric Lee for The New York Times