Leon Wolf at RedState notes that CNN is touting that it has beaten Fox News in the primetime ratings in the key age demographic of 25 to 54 in five of the last eight months. In all-day ratings in that demographic, CNN used to have less than half of Fox's overall viewership, but they now are behind Fox News by nine percent.
CNN's press release noted "The last time CNN had this many prime time wins in an eight-month period versus Fox News was over 14 years ago (Nov. 2001)." Wolf says Trump-boosting is eating into Fox's numbers:
CNN is definitely not without its flaws. They cover Trump way too much, as even their own on-air personalities have been known to observe on-air. However, what’s interesting is that Fox News is clearly suffering the most in their prime time lineup. For the last 8 months, Fox’s prime time lineup has been anchored by a number of personalities (including Eric Bolling, Sean Hannity, Bill O’Reilly, and Greta) who have basically been running barely-disguised Trump infomercials.
The conventional wisdom on the right has been that this approach is the best way to build traffic. The experience of RedState – and now, on the other hand, of Fox News – suggests that this might not be so. You can get a temporary boost, but there’s a low ceiling, because Trump’s actual base of support is quite small (if rabid). In the meantime, you cost yourself (possibly permanently) some portion of your long-time audience.
TVNewser added CNN doesn't just look good among news channels: " In April, CNN experienced the strongest year-over-year growth of any network (cable or broadcast) in both total viewers and adults 25-54 during prime time: +125 percent in total viewers (1.14 mil vs. 507,000) and +105 percent in the news demo (381,000 vs. 186,000) from April 2015."