Across democracies, citizens are increasingly disenchanted with political parties, as evidenced by dwindling support for mass parties and increasing protest and extreme votes, as well as lower rates of party membership and of voter turnout altogether. Parties have become vestigial. The decrease in party identification leads to a reduced acceptance of the presumed legitimacy of state decisions. The paper argues that political parties have originally evolved as a “rational response” to the prevailing historical and institutional circumstances of democratic representation. They discharge the tasks that follow from the system of democratic representation as we have set it up. But they also pose a threat, inasmuch as they display effects that are detrimental to the legitimacy of representative decisions. The paper argues that the current institutional setup thus leads to a “party paradox”: we cannot do without parties, but we cannot do with them either.