Absence has not made viewers any fonder of “Boston Legal.” Ever since the ABC show, booted from the schedule last spring after “Grey’s Anatomy” took off on Sunday nights, returned earlier this month on a new night, it’s been struggling.
   Last night’s episode averaged a 1.5 adults 18-49 rating, according to Nielsen overnights. That’s down 17 percent from a 1.8 during the week it returned to the schedule, Aug. 9, and not even half the 4.9 the show averaged during the regular season.
   No one expected “Legal,” the first-year spinoff of ABC’s long-running “The Practice,” to come anywhere near its regular-season numbers upon its Tuesday debut considering it led out of “Desperate Housewives” last year.
   But a 1.65 average rating for four outings is pretty dismal. 
   “Legal” has finished third in its 10 p.m. timeslot the past four outings, behind CBS’s reality show “Rock Star” and NBC repeats of “Law & Order: Special Victims Unit.”
   “Legal” went off the air with four original episodes still in the can in late March for what was supposed to be a limited engagement for “Anatomy.” “Legal” was supposed to return for May sweeps. But “Anatomy” did so well that ABC kept it in the slot through the May sweeps and pushed the remaining “Legal” episodes into season two.
   It must have ABC wondering whether the show can rebound when the regular season begins next month. The network hoped “Legal” could help bring eyeballs to lead-in “Commander-in-Chief,” the much-hyped new show starring Geena Davis that will air at 9 p.m.
   Based on summer reruns, that may not happen. Both shows premiere Sept. 27.
   CBS easily finished first last night among 18-49s, averaging a 3.1 rating and 8 share. Fox was a distant second at 2.3/6, followed by NBC at 2.0/6, ABC at 1.8/5, the WB at 1.2/3 and UPN at 1.1/3.
   CBS’s improving “NCIS” averaged a 2.4 at 8 p.m. to finish first. NBC’s “Most Outrageous TV Moments” was second with a 2.1, followed by a Fox rerun of “House” at 1.9.
   At 9 p.m., CBS maintained its lead with a 3.6 for “Big Brother.” Another “House” rerun on Fox averaged a 2.6.
   NBC’s “Tommy Lee Goes to College” took a big dip in its third outing, averaging a 2.0, down 23 percent from last week’s 2.6. “Lee” and a repeat of “The Office” averaged a third-place 1.7.
   At 10 p.m., CBS’s “Rock” averaged a first-place 3.2, followed by a 2.3 for NBC’s “L&O: SVU.” “Legal” was last with a 1.5.
   Among households CBS also led for the night with a 5.5/9. Fox was second at 4.6/7, NBC third at 4.2/7, ABC fourth at 3.6/6, the WB fifth at 1.9/3 and UPN sixth at 1.7/3.