In the VIP section of what the Republican party planned as an election night celebration in 2012, big donors including Paul Singer and Joe Ricketts watched the votes trickle in to determine whether Mitt Romney would unseat Barack Obama as US president.A lesser known pair at the event — hedge fund manager Bob Mercer and his daughter Rebekah — had high hopes but it soon became clear Mr Romney was losing. When Fox News called Ohio for Mr Obama, top Romney operatives still insisted they had a chance. Republican strategist Karl Rove disputed the Ohio call on Fox — in...