There's a very special reason why Donald Trump uses this song at the end of some of his rallies

Listen to the words very carefully for those that have not heard them. There's a very special reason why @realDonaldTrump uses this song at the end of some of his rallies and at the end of his acceptance speech at the Republican National Committee.
I HAVE HIDDEN MY SECRETS WELL.
AT DAWN, WE'LL WIN.
WE WILL WIN
WE WILL WIN