The congressman from Ohio is campaigning to be the Democratic nominee for president and to run against President George Bush.
Nelson wrote the song on Christmas Day, debuted it Friday at the concert, and planned to record "Whatever Happened to Peace on Earth" this week in Nashville and rush it into release as a single, the Austin Statesman reported Saturday.
Nelson told the Statesman that he woke up early Christmas morning at his Lake Elsinore, Calif., home of his in-laws and turned on the news.
"There was nothing but bad news, and here it was Christmas Day," Nelson said. "I said, There sure are a lot of babies dying and mothers crying, and (his wife) Annie said, 'That sounds like a song.'"
By the end of the day he had written his second protest song.
Nelson said he became interested in endorsing Kucinich because of the Ohioan's support of family farmers who has also been a critic of the war in Iraq.