Read this passage: A group of migrant farmworkers only employs one lobbyist, so it isn't able to convince many legislators to support its agenda. What possible disadvantage of interest groups does this scenario illustrate?

They lack power unless they are well funded.

Explanation:

Interest groups are organizations that share a concern on a specific subject of social or political relevance. These tend to be formally organized, and their purpose is usually to influence public policy. However, even though they can be quite effective, one of the disadvantages of such groups is that they can lack power unless these are well-funded or supported by other powerful groups.

That if one isn't wealthy, they won't have the proper resources to convince congressmen that their cause is worth defending.