This paper analyzes the relationship between malapportionment and electoral bases of support for Brazilian senators. The conventional wisdom asserts that malapportionment contributes to the “politics of backwardness” – that it facilitates clientelism and hinders issue-based campaigns, reducing electoral competition and producing geographically concentrated patterns of votes. Our study partially confirms, yet partially refutes this wisdom. Our research indicates that malapportionment affects the competitiveness of elections: senators from overrepresented states tend to dominate their key municipalities electorally, whereas senators from underrepresented states tend to share their core municipalities. In addition, underrepresentation increases the likelihood that leftist candidates will be elected. These findings are consistent with the traditional understanding. However, contrary to the conventional wisdom, we find that senators from underrepresented states tend to exhibit geographically concentrated patterns of electoral bases, whereas those from overrepresented areas show much more scattered bases of support. Hence, our findings suggest that the relationship between malapportionment and elections may be more complex than commonly acknowledged.