When and why do electoral commitments enhance parties’ ability to implement their preferred policy in multiparty governments? We propose an audience costs theory whereby strong platform commitments enhance parties’ negotiating positions in multiparty cabinets but only when they are on a salient policy issue for core voters and the party controls the policy-relevant portfolio. Utilizing new data on portfolio allocations in eight parliamentary democracies over 40 years, we show that absent a strong platform commitment, control of the portfolio of social affairs by social democrats, alone, is not associated with changes in welfare generosity. Notably, our findings are independent of party size and hold in most multiparty legislative systems not dominated by three parties.