CNN’s prime-time ratings plunged 26% in April — the cable news network’s worst month for total viewers since October 2015, according to Nielsen Media Research.

The network suffered a 41% slide in viewers aged 25 to 54 — the demographic most coveted by advertisers. And not one of its prime-time shows finished in the top five for news.

CNN’s “Cuomo Prime Time,” which airs during the network’s highest-rated hour, finished in 26th place.

The ratings slide coincides with special counsel Robert Mueller’s report on Russian election interference, which found no collusion between Russia and the Trump campaign — a boon for Trump supporters and a letdown for people who want him impeached.

The WarnerMedia news outlet run by Jeff Zucker drew 198,000 viewers in the 25-to-54 age group, while MSNBC delivered 255,000 and Fox News 389,000.

All three networks saw April declines in the desirable demographic over last year, with MSNBC down 36% and Fox News down 19%.

Fox News also led the pack in prime time, drawing an average of 2.4 million viewers to its top lineup, flat over April 2018.

MSNBC’s prime-time viewership, by contrast, fell 14%, to 1.66 million. CNN’s tumbled 26%, to 767,000.

April’s ratings roundup extended Fox News’ winning streak as the most-watched cable news network — in both prime time and total day — to 208 consecutive months.

CNN’s prime-time viewership, by contrast, fell to No. 15 — behind ESPN, Hallmark Channel, History, TBS and others.

Among prime-time cable news shows, Fox News’ “Hannity” led with a total audience of 3.08 million viewers, followed by FNC’s “Tucker Carlson Tonight” with 2.83 million. MSNBC’s “The Rachel Maddow Show” attracted 2.63 million.

Zucker was named chairman of AT&T’s WarnerMedia News & Sports while remaining president of CNN.