FACTBOX: "American Idol" finalists Adam Lambert, Kris Allen

LOS ANGELES (Reuters) - Flamboyant singer Adam Lambert and clean-cut guitar and piano player Kris Allen sing for the title of "American Idol" on Tuesday in the eighth season finale of the popular U.S. television singing contest.

Lambert goes into the two-part finale on Tuesday and Wednesday as the clear favorite of the show's four judges, while Allen is seen as this season's dark horse and has a huge fan base of teenage girls.

The winner will be announced on Wednesday in a star-studded two-hour finale.

Following are brief profiles of the two finalists.

* Adam Lambert, 27, was raised in San Diego, California, and has a musical theater background that led to a role as the understudy for the part of Fiyero in the Los Angeles cast of the hit musical "Wicked." He is known for his vocal range and falsetto, for putting a new spin on standard songs and for his affinity for black nail polish and eyeliner. His sexual orientation has been a subject of debate since photos of him kissing other men surfaced on the Internet. Sometimes criticized for self-indulgence, Lambert won a rare standing ovation from judge Simon Cowell for his performance of "Mad World" last month. His fans call themselves "Glamberts."

* Kris Allen, 23, is from Arkansas and plays viola and the ukulele in addition to the guitar and piano skills seen on "Idol." A Christian and a worship leader who has traveled overseas as a missionary, he married his longtime girlfriend, Katy, in September 2008. Allen was a business student before auditioning for "Idol" and has no formal singing training. Quiet and unassuming, Allen has won praise for his acoustic versions of rapper Kanye West's "Heartless" and the disco classic "She Works Hard for the Money."

(Reporting by Jill Serjeant)