Ratings: 'American Idol' wins Tuesday as St. Patrick's Day takes its toll on viewership

Honestly, our favorite bit of trivia about Tuesday night's TV ratings is the following, courtesy of an ABC press release cushioning soft numbers for Dancing With the Stars' first elimination night this season: "Due to the St. Patrick's Day holiday, overall primetime TV usage levels were down notably among Adults 18-49 from the prior Tuesday (36.2 percent vs. 37.6 percent). In fact the 18-49 television usage level was the 3rd-lowest for any Tuesday this season, above of only the two weeks containing the Christmas and New Year's holidays...." In other words, look for many shows' final numbers to climb once those young intoxicated adults are sober enough to operate their TiVos. Looking at total viewers in our chart below, American Idol was down 16 percent from last Tuesday. CBS powerhouses NCIS and The Mentalist faced the dreaded Idol/DWTS double whammy -- and took a hit. They both averaged over 15 million viewers Tuesday, but their last original episodes each averaged over 18 million.