GOP debate will showcase CNN, as well as the candidates

CNN expects the biggest audience in its history Wednesday night for the second Republican presidential debate, which presents a major journalistic, technical and business challenge for the Atlanta-based network.

Well before the lights go on, CNN faced controversy in staging the highly profitable two-part, 15-candidate event. It tweaked its rules to move businesswoman Carly Fiorina out of the "kids' table" debate and expand the prime-time field to 11 after Fiorina and her backers complained. But CNN so far has not responded to businessman Donald Trump's request that its profits from the debate's lucrative ad sales — the network is reportedly charging $200,000 for a 30 second ad — go to veterans charities.

The prime draw once again will be Trump. Former CNN Washington bureau chief Frank Sesno, now director of the School of Media and Public Affairs at George Washington University, said the network should try to keep the billionaire from dominating.

"This will be a very important moment," Sesno said. "Because the question will be whether, in the way that CNN conducts the debate, it in any way changes the dynamic, changes the equation, makes it somehow less about Donald Trump and more about the others or the issues."