National Republicans have joined the fight too. White Mountain PAC, an outside group created just last month, has plunged more than $4m (£3.5m) into TV ads boosting Mr Morse into the final fortnight of the campaign. The Senate Leadership Fund, which is controlled by the powerful Senate Minority Leader Mitch McConnell, announced it plans to spend at least $23m in ads in the state through November – although it is unclear if it will do so if Mr Bolduc is the nominee.