I can give you a theory for why Fox News and MSNBC each get more positive buzz than CNN. I’m not sure I can give you a theory for the particular trendline for CNN.

That graph charts responses to the question “If you’ve heard anything about the brand in the last two weeks, through advertising, news or word of mouth, was it positive or negative?” First off, note how rare it is for any of the networks to be net positive in buzz. Fox and CNN have each managed the feat only twice, and briefly at that, over the past 14 months. MSNBC has never managed it. Note too how competitive the three networks were for most of last year — until election time, when perception of CNN’s brand fell off the table. It recovered a bit for awhile in December but struggled to stay above -10 and has begun to sink again lately. How come? If the answer is as simple as “They’re loudly anti-Trump,” why isn’t MSNBC’s buzz garbage too?

Theory: Fox and MSNBC do better than CNN because each aims squarely at a different group of ardent partisans. Fox will always get thumbs up from conservatives and MSNBC will always get thumbs up from liberals, so perceptions of their brand have a built-in buoyancy. CNN, the (supposedly) least ideological network, has no similar cheering section so when people hear something about them in the news, odds are it’s due to some controversy — maybe Trump attacking the network, maybe something the network got wrong, maybe an interview that went sideways. Negative perceptions end up overwhelming positive ones. But … why would CNN’s brand rating have been similar to Fox’s and MSNBC’s for so much of last year and then crumbled right around election day?

Could it be the same partisan effect at work? During the campaign, each network was consumed with reporting the day’s events. Once Trump won the election, though, conservatives thrilled to Fox News’s reporting about how great the next White House would be while liberals thrilled to MSNBC’s coverage of how terrible it would be and how Democrats should resist. Again, without a natural fan base, CNN was left to flail by alienating both sides. If they did a hard-hitting interview with Kellyanne Conway, conservatives would hear about it and bristle; if they did a softball interview with her, liberals would bristle. CNN may be presumed liberal by Fox fans and conservative by MSNBC fans, such that any time it lives up to either stereotype its critics seize on the moment as further evidence that they were right in suspecting bias all along. If that’s true, CNN’s position is no-win. They can’t be antagonistic enough to one side enough to please the other.

But yeah, I think there’s a “Trump effect” too. When the president’s out there calling them the “Clinton News Network” and their otherwise nonpartisan anchors are delivering quasi-special comments about how “un-American” the White House is behaving towards the press, Trumpers will inevitably circle the wagons and conclude that CNN is a special menace that MSNBC isn’t. My sense is that CNN has also landed more damaging scoops about the new administration, most famously the one involving Trump and Obama being briefed in December on the private “dossier” alleging contacts between Team Trump and Russia, than NBC or MSNBC has. As the Times put it, “The old CNN may have shrunk from conflict; the new CNN is leaning into it … vociferously pledging to hold a truth-averse White House to account.” For what it’s worth, though, CNN President Jeff Zucker claims that he conducted his own “buzz” analysis of the network recently and that everything’s hunky dory:

“I have wondered about that, and I frankly was concerned that when you have that constant drumbeat for a year, you know, the president of the United States saying it on a daily basis. I wondered what impact that would have,” Zucker said.

But CNN ordered a major brand study that was conducted throughout the month of January to examine what impact the attacks have had on its credibility with viewers and with the public.

“There has been no diminution whatsoever,” Zucker said the study showed. “The CNN brand is as strong as it has ever been. Incredibly trusted. And we have seen no impact whatsoever in all those attacks on the CNN brand.”

Not what YouGov is seeing, but okay. CNN’s ratings also now trail MSNBC’s in primetime, although not in the 25-54 demographic that’s so important to advertisers. Make of that what you will.

If you missed it on Friday, here’s Shep Smith defending CNN on Fox’s airwaves after Sean Spicer barred them from the press gaggle.