The political landscape of the US has now turned red. States in which the GOP won included North Carolina, Montana, West Virginia and South Dakota. Their majority could increase as Louisiana will hold a run off election early next month.
As well as the Senate the Republicans are projected to increase their lead in the House of Representatives to levels not seen since before World War Two.
When the new Congress is sworn in in January it will mark the first time the Republicans have held both chambers since 2006.