NIKAIA, Greece — For over a year, 30 Kaisareias Street bustled with activity. Burly, black-clad members of the neo-fascist Golden Dawn party converted part of the nondescript white building into a headquarters, holding frequent meetings and fanning out for military-style neighborhood patrols armed with batons and heavy poles wrapped in the Greek flag.

Then, last week, the group disappeared overnight. A regular in the office, Giorgos Roupakias, was accused of killing an anti-fascist activist in a crime that shocked the nation, and the government began an effort to “eradicate” the group, as Prime Minister Antonis Samaras put it.

But already, serious questions have been raised about the planning and effectiveness of the crackdown, and whether it may actually boomerang against the government and end up generating sympathy for Golden Dawn, one of Europe’s most violent far-right groups.

“If it is not handled properly, you could get a kind of a bounce back of Golden Dawn,” said George Katrougalos, a constitutional law professor at the Democritus University of Thrace. “If they appear to be victims of the establishment, that may broaden their appeal.”