Broadcast TV in no man’s land as younger viewers flock to streaming—and boomers turn to Fox News

Two milestones revealed this week illustrate the diminishing power of broadcast television in the media world — one fueled by the habits of young people and the other by their elders.

During June, viewers spent more time watching streaming services than they did for broadcast and cable television combined. That happened for the first time ever in May, by a fraction of a percentage point, but the Nielsen company said on Tuesday that gap widened considerably in June.

Also, for the third straight week...