Trump almost certainly doesn't have a genuine voter base, and, I'm sorry, Ben Carson is a nice social conservative doctor, but he isn't presidential material; he's dyed in the wool physician material and always will be. In a general election debate, Hillary Clinton will leave him looking like a student kept after class.
Not only are Rubio and Fiorina between them packing four sets of brass knuckles with Hillary's name on them, they've both got instant command of every issue that matters, particularly in foreign policy in what will very much be a foreign policy election. There are simply too many foreign pieces already in motion on the board for it not to be.
Plus, Rubio + Fiorina will force fence-sitting independents - the ones who actually decide presidential elections - to decide between two women and two Hispanics (Julian Castro), with the opportunity to pick an Hispanic President lying on the Republican side of the ticket.
Time to consolidate forces.