CNN suffered its worst ratings among primetime viewers in the most coveted demographic by advertisers — dealing a gut punch to embattled new boss Mark Thompson. The cable channel, which touts itself as “the most trusted name in news,” drew just 83,000 viewers aged 25 to 54 during the week of May 13-19 from 8 to 11 p.m. — its lowest-rated week since 1991, according to Nielsen. By contrast, Fox News garnered more than the twice the audience in the...