In 2011, Fox News announced that a new guest would appear weekly on “Fox & Friends,” its chummy morning show. “Bold, brash, and never bashful,” a network ad declared. “The Donald now makes his voice loud and clear, every Monday on Fox.”

It was the beginning of a beautiful friendship.

Seven years later, the symbiosis between Donald J. Trump and his favorite cable network has only deepened. Fox News, whose commentators resolutely defend the president’s agenda, has seen ratings and revenues rise. President Trump views the network as a convenient safe space where he can express himself with little criticism from eager-to-please hosts.

Now, the line between the network’s studios and Mr. Trump’s White House is blurring further. Bill Shine, a former Fox News co-president who helped create the look and feel of the channel’s conservative programming, is expected to be hired as the president’s new deputy chief of staff, overseeing communications.

He was recommended to Mr. Trump by a mutual friend: Sean Hannity, the Fox News star who has become a confidant of the president and promoter of the administration’s message to his average nightly audience of about 3.4 million viewers, the biggest in cable news.