WASHINGTON — (CNN) Airing Thursday’s Democratic debate on two channels, PBS and CNN, appears to have almost doubled the audience.

The PBS-produced debate averaged a 3.3 household rating on PBS, according to overnight data from Nielsen’s metered markets. MSNBC also averaged a 3.3 rating for its Democratic debate at the same time last week, which was considered a weak result.

CNN’s simulcast of the debate averaged a 3.0 rating. Combined, the Democratic debate drew a 6.3 household rating.

The combined rating puts the debate in the middle of the pack of the six Democratic match-ups so far this season.

Six months after the first debate of the 2016 primary calendar, it is clear that there is some measure of “debate fatigue,” more so on the Democratic side than on the Republican side.

The first Democratic debate, televised by CNN in October, had an 11.2 household rating. None of the rematches since then have come close.

Still, debate ratings remain at an elevated level, in many cases above equivalent debates in 2008, the last time there were primaries on both sides.

Thursday’s 6.3 combined rating was higher than the CBS Democratic debate on a Saturday in November, which had a 6.1 household rating, and ABC’s Saturday night Democratic debate in December, which had a 5.7 rating.

It was lower than NBC’s Sunday night debate in January, which had a 7.2 rating.

Actual viewer numbers will be released later on Friday. The combined PBS and CNN broadcast likely reached 8 million to 10 million viewers.

Thanks to Thursday’s simulcast, which was announced last week, CNN was No. 1 among cable news channels for the night, according to the preliminary Nielsen data, just as MSNBC was No. 1 thanks to its debate.

According to the Washington Post, CNN paid a “licensing fee” for access to the PBS debate.

Thursday’s meeting between Hillary Clinton and Bernie Sanders was the first debate ever produced by the “PBS NewsHour.”

Moderators Gwen Ifill and Judy Woodruff were generally praised for their professional questioning.

Time magazine noted that it marked the first time an all-female duo moderated a Democratic debate.

The next GOP debate will be televised by CBS on Saturday night. The next Democratic debate will be on CNN on March 6.

The-CNN-Wire ™ & © 2016 Cable News Network, Inc., a Time Warner Company. All rights reserved. (Photo: CNN)