Parliamentary entry on the national level is a crucial achievement for any new party but necessarily beneficial. To assess the electoral costs of parliamentary breakthrough, we specify factors that shape a)a party’s capacity to cope with new demands and b)the intensity of the demands a new party is exposed to after breakthrough. To test our hypotheses, we apply multilevel analyses to a new dataset covering organizationally new parties that entered national parliament across 17 advanced democracies over a forty-year period. We find that new parties formed by individual entrepreneurs as founding leaders without any ties to already organized groups are less likely to get re-elected than newcomers that can rely on such ties. Furthermore, the electoral costs of parliamentary entry decrease with the time for party building a newcomer had between its organizational foundation and breakthrough.
