Grand challenges are among the most complex problems for modern societies. Many governments and foundations provide substantial resources to encourage the search for solutions. Due to the significance of these problems, organizations often form partnerships in what we call search consortia to engage in joint search and compete for funding. Prior research on joint search highlights the role of specialized organizations, mainly regarding technological domains, to identify a superior solution. However, stakeholder theory leads us to believe that the success of any solution depends on the acceptance and support of important stakeholders. In this study we suggest that search consortia are more likely to receive funding when they include representatives of stakeholder concerns, so-called advocacy groups. We extend theory on coordinated exploration in joint search by integrating mechanisms from stakeholder theory and argue that advocacy groups improve the generation of potential solutions and provide legitimacy. We test our theory with a unique dataset of 35,249 consortia that proposed solutions to 2,349 grand challenge problems as part of a large European funding program. Our results show that advocacy groups benefit search consortia, particularly when consortia exhibit a high dispersion of technological knowledge and when they are inexperienced.