The town hall for Castro on CNN also lost in the ratings to a previously held town hall by the network for Kirsten Gillibrand.
Fox News Channel's primetime viewership numbers beat out the cable news competition once again on Thursday night.
According to Nielsen Media Research's early numbers, FNC bested CNN numbers even during the network's own town hall event, with 2020 Democratic presidential candidate Julian Castro.
Averaging 2.7 million viewers and nearly 500,000 in the 25-54 age demographic, "The Ingraham Angle" numbers more than quadrupled CNN’s town hall in total viewers and almost tripled CNN in the 25-54 age category. CNN town halls brought in 654,000 average viewers and 174,000 in the age range.
CNN’s latest town hall ranked third in both categories and was down 41 percent in total viewers and down nearly 50 percent in the key 25-54 age demo. Thursday night's special event for Castro also marked the second lowest-rated weekday primetime town hall in cable news history.