Washington — Former Gov. Roy Cooper and former Republican National Committee Chairman Michael Whatley are set to face off in November in what's expected to be among the most competitive Senate races of the cycle. Whatley and Cooper won their respective primaries Tuesday night, CBS News projects. The outcome was widely expected, and the two men have effectively been campaigning against one another for months. But with Tuesday's primary victories, the real contest gets underway.Cooper and Whatley are facing off for an open seat representing North Carolina in the Senate after GOP Sen. Thom Tillis announced in June that he wouldn't seek reelection hours after President Trump threatened to back a primary challenge against him.…