As stations across the country begin to fret about the effect Jay Leno's dipping ratings have had on their late-night news shows, ratings figures show the former Tonight Show host may have contributed to an 18-percent drop in viewers for Tampa NBC affiliate WFLA-Ch. 8's 11 p.m. newscast.

This means Leno may have helped cost WFLA first place at 11 p.m., handing the crown to rival CBS affiliate WTSP-Ch. 10.

Among adults 25 to 54, the type of viewers advertisers covet, ratings for WFLA's 11 p.m. news initially rose 10 percent in the first week of Leno's show -- when most other networks were still airing summer series and interest was highest.

More recently, ratings among those viewers have dropped, as Leno's 10 p.m. rating have dropped from a high of 4.3 to the current average of 2.0 -- a 22-percent drop from last year.

This is the outcome Leno critics feared most; that low ratings for his 10 p.m. show would also pull down ratings for the 11 p.m. newscasts which follow on NBC affiliates. For example, while WFLA's 11 p.m. ratings have fallen, rival WTSP-Ch. 10 has seen its 11 p.m. ratings rise 46 percent, likely due to stronger ratings for its popular 10 p.m. dramas such as CSI: Miami and The Mentalist.

WFLA, which was leading the 11 p.m. ratings before Leno's debut, is now in second place, unseated by the new ratings dynamic Leno seems to be leading.

"In the Tampa market, late news historically is very much dependent on the strength of the prime lead-in," wrote WFLA research director Jennifer Yarter in an email to the St. Petersburg Times.

WFLA isn't alone. according to the New York Post: "Ratings for late newscasts at NBC affiliates in 44 of the top 56 metered markets are down this year, falling an average of 13 percent in the first four weeks of the season compared with a year ago. In 10 of the top 25 major markets, the numbers are worse, with New York down 22 percent, Philadelphia off 37 percent and Miami down 30 percent."

And the fallout goes beyond local affiliates: ratings for Leno's successor Conan O'Brien are down 47-percent from last year, about 2-million viewers, when Leno himself hosted, according to the New York Times. Other NBC shows such as Law & Order and Law & Order: SVU have floundered in 9 p.m. timeslots, pushed from their traditional 10 p.m. hours to make room for Leno.

Here's how bad it's gotten; on Monday, an original Leno broadcast scored half the ratings of a re-run of CSI: Miami (among adults 18 to 49, CSI was almost three times as popular), taking wind out of NBC's notion that the comic's show would do better when competing network programs were showing repeats.

Experienced TV hands know that ratings can be a long-term game, especially with talk shows involving hosts well-known as Leno. It's likely NBC will try holding off antsy affiliates until after Christmas, when they can see how Leno's new show do against rivals' moribund holiday schedules.

But take it from CBS, which has yet to see evening news anchor Katie Couric climb out of last place in the ratings game; sometime bad numbers never get better.