The 'linkage' between domestic politics and foreign policy is often discussed in the international relations literature. Yet, we know relatively little about the relationship between domestic politics and peacemaking. Moreover, we know next to nothing about what kind of impact internal party conflicts have on foreign policy. While the literature has attempted to address how the relationship between parties influences peacemaking, it has basically ignored how the internal divisions within parties can affect this process as well. Can intraparty factors encourage or deter a governing party from initiating a peace process? Can peacemaking produce intraparty divisions that will endanger or even foil the peace process? If, in democratic systems, foreign policy is influenced by domestic politics, then it is important to know which domestic actors can exert this influence. This article shows that the government's ability to implement its foreign policy and to elicit popular legitimacy is influenced by the extent of partisan cohesion. This article also points out that intrapartisan politics is an important aspect that must be brought into both international relations and political science research concerning domestic influences on foreign policy in general, and peacemaking in particular. Without this element, even an intermediate range theory on this relationship would be, at best, sanguine, if not incomplete. That is, the analysis of the relationship between domestic politics and foreign policy should not treat political parties as unitary actors. Using the case of the Israeli Labor Party and the Middle East peace process between 1992 and 1996, this article suggests that the peace process had a strong impact on the internal cohesion of the party, and that the internal partisan divisions influenced the peace process. This article, therefore, provides evidence that party cohesion is a necessary variable for successfully promoting a dramatically new foreign policy.