An excellent write-up of where election maps, result graphs, and other common data visualisations used in election reporting most commonly fall down. Missing descriptive text, unassociated labels, inaccessible toggles and interactive elements. Unfortunately doesn't go into much detail on solutions, but interesting screen reader recordings highlight some of the main roadblocks.
On the inherent difficulties with working with data on the web:
Data visualizations typically are inaccessible by default. If we don't actively curate accessibility of our charts, we will end up with visualizations that are varying levels of inaccessible.