Fox News host Glenn Beck may be in denial about his ratings decline, but the Nielsen numbers don’t lie: He’s lost one-third of his audience from this time last year, and has lost nearly four out of ten of his viewers between the ages of 25 and 54, the demographic advertisers most covet.

From TVNewser:

While Glenn Beck and Greta Van Susteren easily made the Top 12, the shows are down the most for the network. Compared to Q1 2010, Beck was down -30% in Total Viewers and down -37% in A25-54 viewers, while “On the Record” was down -23% in Total Viewers and down -28% in younger viewers.

One key difference between Beck’s decline and Van Susteren’s is that between 300 and 400 advertisers have vowed not to be associated with Glenn Beck. Susteren’s show is facing no such boycott.

The latest bad news for Beck comes in the wake of his weak ratings performance in January, when he posted his worst numbers since joining Fox News.

The ratings sag seems to be spreading to Beck’s radio empire as well, where he suddenly finds himself off in key markets such as New York and Philadelphia.

Media Matters. We can only hope that this represents a decline in Wingnuttia itself, but who knows.