NEW YORK - Fox was the most-watched American network last week, ably assisted by its one-two punch from "American Idol."

Right behind, CBS was boosted by its scripted shows, seven of which (along with its "Survivor: Micronesia" and "60 Minutes") landed in the top 20. But third-place ABC had one of the week's most unusual hits: the debate between Democratic hopefuls Hillary Rodham Clinton and Barack Obama.

As with many popular successes, the two-hour debate from Philadelphia was critically lambasted for the performance of its moderators, ABC News' Charles Gibson and George Stephanopoulos. But it drew 10.69 million viewers, ranking as the week's 14th most-watched program (and ABC's fourth-most popular broadcast, after its two editions of "Dancing with the Stars" as well as "Desperate Housewives").

For the week, Fox averaged 8.75 million viewers (5.3 rating, 9 share), while CBS had 8.54 million (5.6 rating, 11 share), according to Nielsen Media Research. ABC had 7.91 million viewers (5.2 rating, 9 share), NBC 7.32 million (4.8 rating, 8 share), the CW 2.29 million viewers (1.5 rating, 2 share), My Network TV 1.01 million (0.7 rating, 1 share) and ION Television 400,000 (0.3 rating, 0 share).

Among the Spanish-language networks, Univision led with 3.48 million viewers (1.8 rating, 3 share). Telemundo had 1.16 million (0.6 rating, 1 share), TeleFutura 540,000 (0.3 rating, 1 share) and Azteca 190,000 (0.1 rating, 0 share).

NBC's "Nightly News" won the ratings race, averaging 8.17 million viewers (5.6 rating, 12 share), while ABC's "World News" had 7.51 million viewers (5.2 rating, 11 share). Trailing CBS' "Evening News" was seen by 5.39 million people (3.7 rating, 8 share).

A ratings point represents 1,128,000 households, or 1 per cent of the nation's estimated 112.8 million TV homes. The share is the percentage of in-use televisions tuned to a given show.

For the week of April 14-20, the top 10 shows, their networks and viewerships: "American Idol" (Tuesday), Fox, 23.65 million; "American Idol" (Wednesday), Fox, 23.34 million; "Dancing With the Stars" (Monday), ABC, 17.20 million; "Desperate Housewives," ABC, 15.75 million; "Dancing With the Stars" (Tuesday), ABC, 15.42 million; "NCIS," CBS, 15.13 million; "Two and a Half Men," CBS, 13.94 million; "CSI: NY," CBS, 13.43 million; "Law & Order: SVU," NBC, 13.27 million; "Criminal Minds," CBS, 12.98 million.

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On the Net: http://www.nielsenmedia.com

Prime-time viewership numbers compiled by Nielsen Media Research for April 14-20. Listings include the week's ranking, with viewership for the week and season-to-date rankings in parentheses. An "X" in parentheses denotes a one-time-only presentation.

1. (1) "American Idol" (Tuesday), Fox, 23.65 million viewers.

2. (2) "American Idol" (Wednesday), Fox, 23.34 million viewers.

3. (4) "Dancing With The Stars" (Monday), ABC, 17.20 million viewers.

4. (6) "Desperate Housewives," ABC, 15.75 million viewers.

5. (8) "Dancing with the Stars" (Tuesday), ABC, 15.42 million viewers.

6. (14) "NCIS," CBS, 15.13 million viewers.

7. (16) "Two and a Half Men," CBS, 13.94 million viewers.

8. (26) "CSI: NY," CBS, 13.43 million viewers.

9. (28) "Law & Order: Special Victims Unit," NBC, 13.27 million viewers.

10. (23) "Criminal Minds," CBS, 12.98 million viewers.

11. (16) "Survivor: Micronesia," CBS, 12.01 million viewers.

12. (58) "Biggest Loser 5," NBC, 11.39 million viewers.

13. (20) "60 Minutes," CBS, 10.75 million viewers.

14. (X) "ABC News: Democratic Presidential Debate," ABC, 10.69 million viewers.

15. (15) "CSI: Miami," CBS, 10.63 million viewers.

16. (28) "Hell's Kitchen," Fox, 10.56 million viewers.

17. (9) "CSI: Crime Scene Investigation," CBS, 10.48 million viewers.

18. (34) "Rules Of Engagement," CBS, 10.40 million viewers.

19. (31) "Oprah's Big Give," ABC, 10.09 million viewers.

20. (34) "Brothers and Sisters," ABC, 10.08 million viewers.