I think they use state and county boards of election data. Example here: https://elections.maryland.gov/elections/2020/results/general/gen_results_2020_4_001-.

I think they use state and county boards of election data. Example here: https://elections.maryland.gov/elections/2020/results/general/gen_results_2020_4_001-.html https://elections.maryland.gov/elections/2020/results/genera...