Common Cause has published this report, explaining that in many states, there are very few choices on general election ballots for state legislature. The report especially singles out eight states in which most state legislative races only have one candidate on the November ballot for state legislature. Those states are Arkansas, Georgia, Massachusetts, South Carolina, Rhode Island, Illinois, Texas, and New Mexico.
This report is very important, because this problem gets virtually no attention from voting rights organizations. Unfortunately, the Common Cause report implies that the problem is caused entirely by gerrymandering. The truth is that the main reason for the lack of candidates are restrictive ballot access laws. Thanks to Thomas Jones for the link to the report.