Lohengrin is the sublime expression of romantic idealism from the very middle of the 19th Century, a musicdrama of thrilling dimension and emotional truculence. As I am wont to see everything as a species of psychognosis, the unconscious intellect, I see the opera as Wagner's inability to love himself.
Elsa represents Wagner's hope and capacity for self-love. Lohengrin represents his artistic calling, his desire to create a spiritually based, unified art-form which is new, but with its roots in the past (myth). For Wagner, this artform must remain inchoate, unnamed and ambiguous, for to pin it down, to name it, would be to squander its power, its majesy and its effect on the subconscious. The tragedy is, Elsa and Lohengrin are incompatible.
The swan knight also represents everything Wagner esteems--his own inner ideal, a sublimity of which he can only dream. For Wagner, it is this curse, the constant striving for perfection, for this ideal which he can never achieve, which fuels his art. He is a divided man, who sacrificed every human principle in answer to his higher calling, and in the service of revolutionary art.