To what extent does party democracy restore faith in democracy itself? This standard political science question dating back to the early studies on party democracy (Roberto Michels, Moisei Ostrogorsky) is raised anew in the context of contemporary American political parties where ‘activists’ are a powerful force. Back in 1962, J.Q. Wilson described political ‘amateurs’ in his well-known study on the Amateur Democrat, in terms that ring especially true for ‘activists’ nowadays: their rise in politics would intensify political conflicts, exaggerate social cleavages, promote rhetorical leadership and make compromises more difficult. Drawing on Polsby (1983), Cohen, Karol, Noel, Zaller (2008, 2016), this chapter tends to show that the collapse of party professionals is illustrative of new tensions hinting at the limits of party democracy. Contemporary factional insurgencies within the parties seem to be the new lay of the political land and it comes at a price: instead of empowering ‘ordinary citizens’, it enables new actors and creates new constraints on people’s will. Relying on secondary sources and newspaper articles, our qualitative analysis concludes that the 2016 cycle demonstrated how parties in the U.S. are in constant danger of being hijacked by their most vocal factions, which is highly detrimental to democratic responsiveness at large. The long-standing distrust against party professionals has paved the way for party innovations that have favored outsiders, clinching presidential nominations through the mobilization of their ad hoc factions. ‘Amateurs’ thus exert a potent pressure, but their rise comes at a cost: a fractious party politics, ‘minority leadership’ and, as illustrated by Trump, an ever-increasing polarization. To that extent, intra-party democracy in the US thus contributed to the weakening of institutional democracy.