Parties and interest groups are known to have organizational ties, such as regular meetings and joint conferences, but little is known about the effect of such ties on interest groups' ability to influence parties in democracies. Given parties' prominent role in such regimes, influencing their positions can be an important step on the way to affecting public policy outcomes for interest groups. Parties are also policy-seeking organizations, however, and they may use ties to interest groups to promote their own agenda. This paper hence asks whether party-interest group ties affect interest group influence on parties as well as mutual party-interest group influence. Using interest group survey data from six established democracies, we examine the relationship between both durable and event-based organizational ties as well as regular leadership contact and perceived influence. We find that interest groups are more likely to influence parties to which they maintain stronger organizational ties. With stronger ties, we moreover find that mutual influence is more common than one-sided influence. This implies that parties are active participants in their interactions with interest groups and that close party-interest group relationships involve give-and-take.
