Among the various challenges facing unions, membership participation and workers empowerment by tools of direct participation within management concretely challenges the ability of unions of representing the diversity of workers' interests. Indeed, a participatory management involves a redefinition of the unions' strategies. Should union blame this trend of direct participation? Recently, these questions were concretely asked to the CGIL-FIOM union, in Italy. In 2010 and 2011, the direction of the Fiat Company decided to use referenda, in order to avoid the refusal of CGIL-FIOM to sign a new agreement about labour conditions in three Italian factories. The direction of the Fiat Company promised, in case of approval by workers, to maintain industrial activities and, in case of refusal, to close these factories. Consequently, the unions were confronted to as strong dilemma: what is the best way to react to this direct participation of workers? Our research about these three referenda is focused on the link between direct participation, public debate and unions' strategies. We present an argument in two main steps. Firstly, we want to show how unions have progressively inverted the democratic sense of these referenda: instead of giving voting instructions, they have chosen to indirectly fuel the public debate, by diffusing arguments and ideas towards workers. The direct participation of workers was used by unions to adopt a "deliberative" activism, to convince workers to resist. Secondly, we also questioned the limits of this strategy: whereas the rates of refusal were surprisingly high within the two firsts referenda, the workers finally decided to support the agreement for the third referendum. These high levels, indirectly supported by unions, have finally frightened the workers, who feared that their factory were definitely. It opens a discussion about the ability of unions to act efficiently within the public debate.