A post on mvictors discusses whether The Victors was "ripped off" from the 1898 march "Spirit of Liberty" by George Rosey.
The short and insufficient answer: The second trio of Spirit of Liberty sounds very similar to the trio of The Victors.
Listen for yourself around the 1:40 mark:
But does this constitute "ripping off," to use the parlance of our times? Interestingly, the song can be found on the album "Karussells of Europe," where its Amazon listing describes Spirit of Liberty as "traditional carousel tune."
Some guy on a forum posed the same question to the Library of Congress via their "ask a librarian" function, and got this answer:
"The Spirit of liberty march" was composed by George M. Rosey (AKA Rosenberg) and it was published in 1898. "The Victors" march was composed by Rosey's friend, Louis Elbel in 1899. The trio of "The Victors" is similar to the last section in Rosey's march which had been written a few months earlier. The two composers were reported to be good friends and the arrangement [Elbel's trio] was presumably made by mutual agreement.
Guy on a Forum isn't exactly a rock of journalistic integrity, but the LoC librarian gave his source as William H. Rehrig's "The Heritage encyclopedia of band music", published at Westerville, Ohio by Integrity Press, vols.1-2, in 1991, with a supplemental vol. 3, published in 1996.
So, yes, most of the melody of the chorus of The Victors is the same as the Spirit of Liberty march. Whether this constitutes deliberate plagiarism is largely irrelevant and debatable, both on the grounds that they were friends, and that this happened before the 1909 Copyright Act was passed.
Supposing it were corrected, it would be "The Victors, music by Louis Elbel and George M. Rosey, lyrics by Louis Elbel." Or, "The Victors, music by Louis Elbel, chorus inspired by a trio from "The Spirit of Liberty March" by George M. Rosey, aka Rosenberg, lyrics by Louis Elbel." Regardless, the lyrics are Elbel's, Rosey never called him out on it, and may have in fact given Elbel his blessing. If the Easter Bunny is dead, it's a good thing he gave his friend the recipe for Peeps a hundred years ago.