All three cable networks have seen their ratings go up during the presidential primaries, but among the “money demo,” Fox News is falling behind. (via TP)

The political season continues to be very good to CNN, which will officially announce on Tuesday that for the first time since 2001, it managed to beat the Fox News Channel in prime time for one quarter of the year in the category of news viewers most desirable to advertisers, according to Nielsen.

Thanks to its debate coverage and heavy focus on the presidential primaries, CNN’s ratings in prime time for viewers 25 to 54 were up 90 percent, to an average of 453,000 for the first quarter of 2008. That was enough to edge past the perennial leader, Fox, which had 438,000 viewers, up 12 percent from last year. MSNBC also had a strong quarter in prime time, growing 68 percent to 329,000 viewers. CNN has done especially well on the nights of contested primaries, winning every night in those ratings except one, the Florida primary on Jan. 29. That was the only night when the Republican race was of higher interest than the Democratic one, and Fox won that night.

Among total viewers, Fox News still leads, but hasn’t shown a lot of room for growth beyond its Republican base. Over the last year, FNC’s ratings have gone up 14%, while MSNBC has gone up 59%, and CNN has seen a 67% increase.

Given this, having Democrats win the White House, Senate, and House may be the best thing to ever happen to the Republican network.