: a person who sympathizes with and often furthers the ideals and program of an organized group (such as the Communist party) without membership in the group or regular participation in its activities.
I recall from many decades ago, “fellow travelers” was a euphemism for commie.
They’re trying to hide it on a google search but if you dig you’ll find it.
“In the post–World War II era, "fellow traveler" became a term of derision, applied by conservatives to people who were communists in all but party affiliation.“
I might sound antiquated. But words matter. See my tagline.