Adversarial (win-lose) negotiation is viable when buyers can leverage abundant alternatives and substitutes, reducing supplier power. In such cases, buyers can adopt tough tactics, knowing they can switch suppliers if necessary. By contrast, limited supply, single sourcing, or monopolist suppliers constrain buyer power, making adversarial strategies risky and often ineffective. CIPS stresses that negotiation style must be matched to market conditions and the power balance.
Reference: CIPS L4M5 (2nd ed.), LO 1.1 - Adversarial negotiation: when power asymmetry favours the buyer.