The article revisits the negotiations on NORDEK, a Nordic Economic Area, held by Denmark, Finland, Iceland, Norway and Sweden in 1968-1970. Finland, which initially took active part in the negotiations, later reversed its position under pressure from the Soviet Union as well as for other reasons. Four remaining Nordic countries refused to pursue a Nordic Economic Area without Finland for multiple reasons, of which one was solidarity with Finland. This article presents multiple game models, of which some reflect the actual outcome of the NORDEK negotiations, i. e., their failure, while others reflect hypothetical outcomes of the negotiations, such as emergence of a NORDEK of four without Finland. Those models allow concluding on the main factors causing Nordic solidarity, for which the NORDEK negotiations were a testing ground, and which had been the defining feature of regional politics in the European North during fifty years following the failure of the negotiations. First, domestic uncertainty about the issue debated by multiple nations contributes to greater solidarity among those nations. Second, majority’s focus on their absolute gains during international negotiations contributes to greater solidarity among negotiating nations. Third, relative equality among negotiating nations does not have any influence on solidarity among them. The latter conclusion supports the theoretical assumption that that organic solidarity (solidarity among different) is as possible as is mechanical solidarity (solidarity of similar).