NBC News is scrambling to defend “Meet the Press” anchor David Gregory amid dismal ratings and swirling rumors that he could be axed as host. The Sunday morning flagship and the longest-running show on network television has recently fallen to a 21-year ratings low, according to Mediaite. Nielsen data show it is averaging its smallest total viewer audience, 2.9 million, in 21 years and smallest 25-to-54 demo performance (854,000) in more than 21 years. CBS’s “Face the Nation” is now the top show in the slot with ABC’s “This Week” second. A network source told Page Six, “There is a rumor that Gregory could be replaced as a host. The fact that his executive producer Betsy Fischer Martinwas recently moved out puts him next in the firing line. The new president of NBC News, Deborah Turness, will have to tackle the ‘Meet the Press’ ratings problem head on.” An NBC News spokesperson insisted, “There is absolutely zero truth to this. David Gregory and ‘Meet the Press’ have the full faith and support of NBC News.” A source added that Gregory “has a long-term commitment with the network” and renewed his contract earlier this year with NBC News (which doesn’t prevent the network from moving him into a different role, say other sources). And Gregory’s new executive producer Rob Yarin is just two weeks into the job after Fischer Martin was “promoted to a larger role within NBC News.” We are told that things were so tense between Gregory and Fischer Martin before she left that they “had to hold separate staff meetings because they couldn’t bear to be in the same room together.”