Former North Carolina Governor Roy Cooper has defeated Republican Michael Whatley to win the state's open US Senate seat, flipping a key Republican-held constituency for Democrats. Whatley, the former Republican National Committee chair, had Donald Trump's endorsement. The seat became vacant after Republican Senator Thom Tillis decided against seeking re-election. Cooper's victory marks Democrats' first major Senate pickup of election night and could prove significant in their efforts to regain control of the US Senate.