Under ideal circumstances, specials provide a spark to a network’s ratings, boosting a troubled time period and briefly capturing the audience’s attention. But in the dog days of this unending summer, most of the specials are diminishing the already low ratings, scoring poorly and dragging their lead-outs down as well.

The prime culprit of late has been ABC, which is trotting out programming that is special only in the sense that it’s not regularly scheduled.

On Wednesday, Aug. 2, ABC’s “Grownups” special managed only a 9.4 rating and 16 share in the 9:30 time period, marking a 20% drop from its “Grace Under Fire” lead-in of 11.7/21.

This was especially disruptive to “Primetime Live.” The previous week, ABC’s regularly scheduled “Roseanne” repeat earned an 11.4/20 at 9:30 and “Primetime” snagged an impressive 13.4/20. But hindered by “Grownups,” “Primetime sank to a 10.5/19 in the 10-11 period on Aug. 2. (The same night, NBC’s “Too Good to Be True II” mustered only a 6.0/12 from 8-9 p.m., finishing a distant third in households.)

On Monday, July 31, ABC slid “Off Camera With Dean Cain” into the 8-9 p.m. block. The show earned a dismal 5.4/10, more than 14% below what Major League Baseball had earned in that first hour the previous two Mondays. (The lack of continuity also damages the networks’ baseball franchise, but that’s another story.)

However, “Off Camera” spent its time more successfully than “Time Well Spent,” ABC’s filler on Saturday from 8-9 p.m. “Time’s” dismal 2.9/7 effectively derailed any hopes for success its lead-out “The Computer Wore Tennis Shoes,” 5.3/11, might have had. The family movie started with only a 4.1/9 before building to a 6.3/13. That same night, NBC received a decent performance from its two specials, even though both were repeats. “World’s Greatest Magic” won every half-hour from 8-10 p.m. with a respectable 6.4/14 and “Abbott & Costello Meet Seinfeld,” 6.2/13, finished second to CBS’ regularly scheduled “Walker, Texas Ranger,” 8.5/18.

The most disappointing special was ABC’s Friday July 28 effort, a half-hour “Michael Jackson Changes HIStory” special. The promotional vehicle’s 6.6/13 marked a 21% fall from a repeat of “Step by Step.” (Fortunately for ABC, in this case, the lead-out – “20/20″ – seemed unaffected, garnering a 13.7/27.)

That is not to say that running tired old episodes of dramas is going to attract more viewers: On Wednesday, Aug. 2, CBS earned a mere 4.4/8 for a rerun of “Northern Exposure,” while Fox’s “Party of Five” scored a dismal 2.9/5.

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