No series could dream of toppling game 1 of the NBA finals, but the debut of Swingtown — CBS’ period piece about swinging couples in the ’70s — managed to not only build on a CSI rerun among adult demos last night, but it also clobbered the premiere of Fear Itself on NBC. Swingtown came in second in its 10-11 p.m. timeslot with 8.5 million viewers, besting Fear Itself by 64 percent (5.23 million), and also ranked second in the timeslot among adults 18-49 and adults 25-54 behind ABC’s Finals, improving the timeslot by 17 percent over this time last year in 18-49. CBS knew its high-profile summer show would have a tough debut: the drama was up against the much-touted opening game of a Lakers/Celtics Finals series taking place on the east coast (ratings for which are not yet available). Things won’t be any easier for Swingtown next Thursday, when ABC airs an L.A.-hosted game 4.