The former Republican congressman was supposed to spice up this season of 'Dancing With the Stars,' but it hasn't worked out that way. In fact, the dance-competition show, a bulwark of ABC's schedule, is shambling through its worst season since it premiered in the summer of 2005. DeLay -- who created a mild sensation during premiere week when he and partner Cheryl Burke did the cha-cha to 'Wild Thing' -- dropped out last week because of injuries, joining Debi Mazar, who was voted off. That will leave this season's fate in the hands of remaining luminaries including Donny Osmond, Kelly Osbourne and Melissa Joan Hart. The ratings pose a worry for ABC, which has been helped through some difficult times by 'Dancing.' Last year, when executives brought back several second-season scripted series that tanked, the ballroom dance-off helped keep ABC competitive overall -- in fact, the network was ranked No. 1 among young adults at this point in the season. Now, ABC is locked in a virtual three-way tie for first with CBS and Fox, and further declines for the show could spell real trouble. Even though the network has seen some encouraging signs with new comedy series 'Modern Family' and 'The Middle,' the unexpected problems for 'Dancing' are creating headaches. All series suffer viewership erosion over time, of course, and compared with most prime-time shows, 'Dancing' still pulls enviable numbers, with an average of 17 million viewers, according to the Nielsen Company. But that's a dip of 13 percent compared with the same period last year. Among adults ages 18 to 49, the viewers advertisers care about most, the show has slipped 19 percent, to a 3.8 average rating. During fall 2007 -- crowned with highlights that included Osmond's sister Marie passing out as the judges critiqued her samba -- 'Dancing' leaped to its most-watched season, averaging 21.7 million viewers. And in fall 2006, the show high-kicked to a 5.8 rating among young adults. (Those record figures, however, include DVR viewing as long as one week following the initial broadcast; those statistics are only just starting to roll in for this season.) So what happened? Neither executive producer Conrad Green nor an ABC executive would comment, according to a network spokeswoman. Privately, ABC officials concede that, the competition, particularly from Fox's hit medical drama 'House,' is much stronger this year. But many analysts and fans believe the cast -- which hews to 'Dancing's' time-tested formula of faded stars, pro jocks and bizarre wild cards -- simply hasn't gelled this year. The inclusion of DeLay, a fiercely partisan former House majority leader who left Congress following indictment on campaign-finance charges in 2005, touched off a flurry of amused interest from the Washington Beltway commentariat. Many ordinary viewers, however, probably had no idea who he was. According to Diageo/Hotline poll taken in February 2006, 24 percent of respondents said they had never heard of DeLay -- and that was at a time when his name was in the news much more than it is now. Other cast members, including Osmond and Hart, likewise owe whatever renown they still possess to achievements years since passed. Hart's 'Sabrina the Teenage Witch' ended its ABC run nearly a decade ago (although it later ran on the WB). 'This cast probably is not as interesting as the casts they've had in the past,' said Scott Sternberg, a reality producer and 'Dancing' fan who is not affiliated with the show. 'You have to connect with one of the players and root for them.' It also hasn't helped that the cast members have been reasonably well-behaved, not what viewers usually look for on an unscripted competition show. During Season 7, Cloris Leachman, then 82 and the show's oldest contestant, endeared herself to viewers with scandalous antics, including grabbing the crotch of partner Corky Ballas during the mambo. This season has had few moments that compare. DeLay, known as the Hammer for his aggressive manner as a politico, managed only a few mild gibes, including a joke that despite Burke's direction, he was having a hard time 'going to the left.' Last week, Osmond tried to shake off his wholesome image by taking judge Bruno Tonioli for a spin on the floor and trading innuendo-laced wisecracks. Viewers were less than charmed. 'This is the worst season ever,' a comment on a Los Angeles Times' message board said last week. 'Now I can go to bed early on Monday and Tuesday nights. Thanks for the extra beauty sleep.' But Andy Donchin, an executive vice president at New York ad company Carat USA, warned that it's too early to write off 'Dancing.' 'It's still an extremely attractive show,' he said. 'I still have six or seven clients in it, and I still see it as a premium program. ... Most shows show a little bit of a decline in the ratings after awhile.' Sternberg said that 'Dancing,' like 'American Idol,' might have reached the point where it needs some rejiggering -- something beyond, say, hiring an out-of-work politician. He suggested more taped pieces showing the dancers rehearsing and giving cohosts Tom Bergeron and Samantha Harris more to do. 'You need to mix up that formula a little bit, freshen things up,' he said. 