Here’s what we know about the ‘American Idol’ farewell

“It’s going to be the closest race in ‘Idol’ history,” “American Idol” judge Keith Urban announced after La’Porsha Renae and Trent Harmon gave their final performances on the opening night of the long-running competition’s two-part swan song at the Dolby Theater.

And Urban’s prediction isn’t off base.

The race for the final “Idol” title -- the show is ending its 15-season run on Thursday -- is an incredibly tight one. It’s down to Renae, the 22-year-old powerhouse songstress, and Harmon, the 25-year-old soulful crooner (both hail from Mississippi).

During Wednesday’s show, the last competitive rounds in “Idol” history -- the finalists (20-year-old rocker Dalton Rapattoni placed third) debuted what will serve as their coronation song and their post-”Idol” debut single if they win.

FULL COVERAGE: Saying farewell to ‘American Idol’

Harmon sang a smoldering, blues-inflected track called “Falling.” The track, which Urban helped co-write, is a departure from the show’s signature inspirational crowning song by taking a sexier, aggressively radio-friendly approach.

“I just keep falling for you baby / You just keep killing me one kiss at a time / Ain’t nothing now that’s gonna save me / Your sweet love keeps calling / And I just keep falling,” Harmon sang to a rapturous standing ovation.

Renae’s track, a powerful ballad titled “Battles,” was equally well received.

Written by rising pop singer Who Is Fancy, Renae’s potential tune sticks closer to “Idol’s” ethos. It packed a deeply personal punch, too, with the song’s inspirational message seeming tailored made for the singer who has spoken openly about surviving domestic abuse and struggling as a single mother. Who Is Fancy later revealed he was inspired to write the song as a tribute to his friend, former “X Factor” contestant and G.R.L. member Simone Battle, who took her own life in 2014.

Long considered the front-runner in the competition, Renae received a massive endorsement Wednesday night after the inaugural “Idol” winner announced she was rooting for Renae to win.

“I have never voted for anyone on [“Idol] not even 4 myself BUT I will be voting for [Renae] tonight. I need her future record!” Kelly Clarkson tweeted on Wednesday.

It’s anyone’s guess who will win the final season of “Idol” but producers are promising the show is going out with a bang.

Here’s what we know:

A virtual who’s who of the “Idol’s” 15-season run has been assembled for the show’s two-hour finale.

Its most famous, and successful, winners Clarkson and country-pop megastar Carrie Underwood will perform (Clarkson, whose second child is due any day now, reportedly pre-taped her performance).

So will every single winner in the show’s history; Ruben Studdard, Fantasia, Taylor Hicks, Jordin Sparks, David Cook, Kris Allen, Lee DeWyze, Scotty McCreery, Phillip Phillips, Candice Glover, Caleb Johnson, Nick Fradiani.

And that’s not it. The winner’s will be joined by a slew of memorable alumni.

Ace Young, Allison Iraheta, Amber Holcomb, Blake Lewis, Bo Bice, Brandon Rogers, Bucky Covington, Carly Smithson, Casey James, Chris Daughtry, Clark Beckham, Clay Aiken, Colton Dixon, Constantine Maroulis, Danny Gokey, Diana DeGarmo and Elliott Yamin will be there.

As will George Huff, James Durbin, Jessica Sanchez, Josh Gracin, Joshua Ledet, Justin Guarini, Katharine McPhee, Kellie Pickler, Kimberley Locke, Kree Harrison, LaToya London, Lauren Alaina, Melinda Doolittle, Pia Toscano, Sanjaya, Skylar Laine, Tamyra Gray and more.

“It’s gotta be entertaining. We’ve gotta pay respect to the legacy, and crown a winner -- and there’s loads of performances,” “Idol” executive producer Trish Kinane said of the finale.

Past male winners Fradiani, DeWyze, Phillips, Allen and Cook will be performing a David Bowie tribute.

Over the weekend Fantasia shared rehearsal footage of Ledet, Doolitle and Beckham singing a gospel hymn. The R&B star is rumored to have taped a performance with Hudson and London -- known as “The Three Divas” during their season three run -- and on Wednesday she announced she will debut her new single, “Ugly,” on Thursday’s live show.

Judges Jennifer Lopez, Harry Connick Jr. and Urban will be taking the stage to sing as well. Lopez will debut a new single, “Ain’t Your Mama,” on the show.

During a recent visit to “Idol’s” set, the show’s associate musical director-vocal coach Michael Orland said he was most excited for the alumni medley’s that are planned.

“It’s going to be insane. I just can’t believe all the people who have come through here,” he said. “The reason the show has lasted so long was it was more than just a TV show. Nobody is going to be able to top what ‘Idol’ was.”

But how will it end? We won’t spoil it but it’s sure to be an emotional moment -- and some people have waited a lifetime for a moment like this.

gerrick.kennedy@latimes.com

For more music news follow me on Twitter: @gerrickkennedy

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