"I'm sorry, I don't even know what to feel right now. This is crazy," said the 23-year-old from Conway, Ark., as he leaned on host Ryan Seacrest to keep from staggering.
Allen's smooth vocals and boy-next-door image gave him the edge after nearly 100 million viewer votes were cast, turning the theatrical Lambert into the most unlikely of also-rans. When the season started, Allen seemed unsure he had a right to take center stage, let alone stand there and snatch victory from such a formidable rival.
During his "Idol" audition last summer, Allen, hands in his pockets and a newsboy cap pulled down around his eyes, was asked by the judges if he was the best singer around.
"You know, there's probably people who are better than me," was Allen's response, offered in the quiet, low-key spirit he retained despite his growing profile.
Conversely, Lambert's commanding vocal range and stage presence - and the judges' lavish adoration - at times turned "Idol" into "The Adam Lambert Show," with the other contestants mere guests. But it turned out that "Idol" viewers could embrace a gifted performer like Lambert, one who sported black nail polish and bold self-assurance, only to a point.
Cowell tipped his hat to both contestants Wednesday night, who shared a moment of musical camaraderie when they joined with Queen on the rock anthem "We Are the Champions."
"To both of you, and I don't normally mean this, I thought you were both brilliant ... the future's all yours," the judge said.
"Adam did win. So did Kris. Nobody lost tonight. These are two champions," said Kiss guitarist Paul Stanley from backstage.
The comments from Cowell and Stanley aren't necessarily empty platitudes. Past contestants can testify that losing the title doesn't mean you're a loser, nor does winning mean you're a shoo-in for superstardom.
Chris Daughtry and Jennifer Hudson, who finished fourth and seventh in their respective seasons, have gone on to huge success. As for "Idol" winners, they range from blockbuster artists like Carrie Underwood to the mostly under-the-radar Taylor Hicks.
Backstage, Lambert was asked about how his second-place finish would be interpreted online.
"The blogs have a lot of opinions, don't they?" he said, smiling and looking relaxed.
His own interpretation?
"I think Kris won because he's a great artist and I was happy to be runner-up to that," he said.
Wednesday's outcome echoed last year's contest, which also looked at the outset like it was going the other way. Cowell all but crowned David Archuleta after the performance finale, calling his a "knockout performance" - but the victory went to David Cook.
Lambert was such a powerful, unique performer that his fans were allowed a sense of entitlement on his behalf. But his triumph wasn't inevitable. When Allen and Lambert were declared the finalists last week, just 1 million viewer votes separated the pair out oing the result until the final minutes. There were group numbers, the Golden Idol Award - semifinalist funnyman Nick "Norman Gentle" Mitchell among the contenders - and celebrity-contestant combos.
Allen was joined by Keith Urban on "Kiss a Girl," while Lambert stomped the stage in elevator boots and oversized ribbed shoulder pads for a pyrotechnic performance with Kiss.
The female finalists, including Allison Iraheta, opened up for Fergie, who sang "Big Girls Don't Cry" and then was joined by her group, the Black Eyed Peas. Iraheta later dueted with Cyndi Lauper on "Time After Time" and Danny Gokey joined Lionel Richie for two tunes.
Rod Stewart sang "Maggie May" after the male finalists opened for him with "Do Ya Think I'm Sexy."
An offbeat guest was Steve Martin, the actor-comedian who also specializes in the banjo. He played his song "Pretty Flowers" with finalists Megan Joy and Michael Sarver on vocals.
Asked by Seacrest to guess who might win "American Idol," Martin replied: "I know it's a long shot, but I'm hoping I do."
Allen rose to the occasion during Tuesday's performance show, especially with his soulful version of "Ain't No Sunshine." But he was tripped up by "No Boundaries," a power ballad song co-written by judge Kara DioGuardi and ill-suited to his voice.
(One audience wag said the tune's exhortation - "You can go higher, you can go deeper ... Every step you climb another mountain" - made it ideal for a Stairmaster exercise machine ad.)
Lambert did a better job with "No Boundaries" and excelled on his reprise of "Mad World" and on "A Change is Gonna Come."
"That was the best I've ever heard you sing - ever!" exclaimed Abdul.
But it wasn't good enough for "American Idol" voters.
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