Tonight's battle between American Idol 2 finalists Clay Aiken and Ruben Studdard will be an all-out war to win the hearts of America -- and be crowned the nation's newest singing sensation.

About 20 million viewers are expected to tune in to tonight's AI2 episode.

Following tonight's show, viewers will vote for either Studdard or Aiken via an 800 number -- with the winner announced in tomorrow night's two-hour finale.

Aiken, the fresh-faced kid from Raleigh, N.C., and Studdard, the bearish fan favorite from Alabama, will sing three songs apiece -- including a tune the winner will release as a single.

The names of those songs are being kept under wraps in anticipation of tonight's show, serving to heighten the suspense.

There are several other changes in store for tonight's episode. Unlike past AI2 episodes, for instance, there won't be any particular theme for tonight's show (disco and R&B were two of the previous themes).

And, as of late yesterday, plans did not include a celebrity judge. In past episodes, Gladys Knight, Olivia Newton-John and Lamont Dozier have critiqued the contestants along with regular AI2 judges Simon Cowell, Paula Abdul and Randy Jackson.

Another change: The phone lines allowing viewers to vote for either Aiken or Studdard will be kept open an hour longer than usual -- closing three hours after the end of tonight's show.

Tomorrow night's show will reunite all 11 AI2 finalists, with Kelly Clarkson, who won the first American Idol competition last summer, performing her single, "Miss Independence."

Tomorrow night's show will also feature remotes from the hometowns of both Aiken and Studdard as friends and family cheer them on.