The baseball playoffs maintained a modest Nielsen batting average over the weekend while Ross Perot proved his first paid political ad was no fluke, drawing an OK 18 share with his chart-and-graph show Friday on ABC.On Saturday, meanwhile, network shares again plummeted across the board, apparently hurt in part by a two-hour Michael Jackson special on HBO. No ratings were available for the HBO special but the three webs combined for a subdued 37 share from 8-9 p.m., again being clubbed by Fox Broadcasting Co.’s “Cops,” with a 17 share in that hour. CBS finished a close second in the metered markets both Friday and Saturday with baseball following lead-off sitcoms “Golden Palace” and “Frannie’s Turn,” respectively. The national pastime is running close to last year’s rating levels at this point but could use another seven-game affair to really shine in terms of ratings and revenues, such as the 30-plus shares for last year’s Game 6 and 7 Atlanta-Pittsburgh showdowns. ABC won Friday thanks to news magazine “20/20,” as the network averaged a 13. 8 rating, 24 share for the night compared to CBS’ 11.9/21 and a 7.1/12 for NBC, which has already charted lineup changes (Daily Variety, Oct. 9). ABC moved struggling freshman sitcom “Camp Wilder” to 9 p.m. and captured a 21 share opposite baseball–its best results yet but also a 4 share drop off its “Step by Step” lead-in. The half-hour Perot ad, in fact, looks to have equaled any performance by the ABC Prods. sitcom at 9:30. NBC narrowly topped CBS in Saturday’s overnights, 9.8/17 to 9.6/17–a lead that could easily be erased in the national standings. “The Commish” helped salvage some respectability for ABC’s nightlong average (7.5/13) but couldn’t prevent a fourth-place 8-10 p.m. finish. Last Thursday’s Oakland-Toronto game popped an 11.8/21 nationally and placed CBS second for the night behind NBC, which nevertheless saw “Rhythm and Blues” (9.2/15) take another precarious dive off “A Different World” to finish fourth in its half-hour and “The Simpsons” cruise to another win at 8 p.m. Across the dial, ABC’s “Room for Two” (10.2/17) had a back-from-the-dead type performance, building on its “Delta” lead-in for the first time in four airings to score its best numbers this season.