For starters, the song is in the key of D natural. I don't know what key Harvey Watkins Jr. did it in with Ruben Studdard though. The song follows basic quartet format and goes like this:
1 2 3 4 1 2 3 4
D A D A
1 2 3 4 1 2 3 4
D A D A
1 2 3 4 1 2 3 4
G G
1 2 3 4 1 2 3 4
G G
That is the bass line, the chords fall in line with the bass line and they all are major chords. The verse and chorus follow the same pattern, however the end stays on that D chord with the bass line bouncing from D to A. THe key can go up or down to C# or Eb. Just move the notes and chords up a half-step or down a half-step.
Be blessed, 'Fred