Called The Challenger, it was the only thing published by The Interfaith Committee Of The Protestant Digest, Inc and it's mission statement, as spelled out in the first issue, was that it would be “a magazine pledged to fight race prejudice, discrimination and all other forms of fascism in North America."
Featuring artwork by the likes of E.C. Stoner, one of the few African-American comic books artists at the time, Bob Fujitani and a 19 year old Joe Kubert, the comic featured the adventures of Bill Day, who Having, along with thousands of other Americans, participated in taking down fascism in Europe is dishearten on returning home to find that it is alive, well and active in the States.
Deciding to do something about it he calls himself the Challenger and travels the nation fighting American Fascists, race haters, union busters, and hate mongers. He also creates the Challenger Club to bring like minded people come together for his cause. Having no special skills or abilities The Challenger just shows up where he finds himself needed and keeps at it until he makes a difference. At the conclusion of which he makes a speech.
As was the case with other prejudice fighting heroes of the time (see DC comics Johnny Everyman and Fawcett's Radar the International Policeman) The Challenger shunned a superhero type costume and instead wore a snap-brim fedora and trench coat, however unlike many mystery men of the time he was not adverse to carrying heat, with his adventures usually featuring at least one running gun battle with the forces of bigotry.
Along with The Challenger each issue also featured at least two or three general non continuing character stories about understanding overcoming hate, such as `Prejudice' by Bob Fujitani, found in issue # 3 which dealt with Japanese Americans encountering bias in post World War II America, and in a story by Joe Kubert a downed American solider behind enemy lines being told the story of the Golem by the Jewish family hiding him, along with some run of the mill humor strips about nothing much in particular to fill out the rest of the four issues that made up this unique experiment in comics.
As for how many kids joined the Callenger Clubs of America, if any did, that I am afraid is a stitistic that will have to remain lost to history.