Results & measures · Presidential election results
Two-party vote share
A party's share of just the Democratic + Republican votes, excluding everyone else.
Two-party vote share divides one major party's votes by the Democratic and Republican votes combined, ignoring third-party, independent, and write-in votes. By construction, the Democratic and Republican two-party shares always add to exactly 100%.
It's the cleanest measure for comparing elections across years, because the third-party vote varies enormously — nearly 19% of the 1992 vote went to Ross Perot, while recent elections have run under 2% 'other'. Raw vote shares absorb that noise; two-party share removes it.
Also known as: two-way vote share, major-party share.
Data: MIT Election Data & Science Lab, Harvard Dataverse.
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Two-party vote share — FAQ
What is two-party vote share in election results data?+
A party's share of just the Democratic + Republican votes, excluding everyone else. Two-party vote share divides one major party's votes by the Democratic and Republican votes combined, ignoring third-party, independent, and write-in votes. By construction, the Democratic and Republican two-party shares always add to exactly 100%.
Why does two-party vote share matter?+
It's the cleanest measure for comparing elections across years, because the third-party vote varies enormously — nearly 19% of the 1992 vote went to Ross Perot, while recent elections have run under 2% 'other'. Raw vote shares absorb that noise; two-party share removes it.
Where does this election data come from?+
All figures come from the MIT Election Data and Science Lab (MEDSL), published on the Harvard Dataverse — state-level presidential returns 1976–2024 and county-level returns 2000–2024. pumsdata is an independent product that makes the data easy to map and compare, and is not affiliated with MEDSL or Harvard.