How are Electoral Votes Allocated?
Each of the 50 states receives electoral votes equal to its total congressional (Senators + Representatives) delegation. Since all states have two Senators and a minimum of one congressional district, the fewest number of electoral votes a state can have is three. Although not a state, the District of Columbia (DC) receives 3a electoral votes. Therefore, the total electoral votes is 538, reflecting 100 Senators + 435 Representatives + 3 for DC.
The number of congressional districts in each state is determined by its Census population. The last Census was in 2010, the next will be in 2020. Once each state’s Census population is finalized, a calculation (called The Method of Equal Proportions) generates the new number of districts for each state. Since the number of districts is fixed by law at 435, states essentially gain or lose representation (and electoral votesb) based on population change relative to the total change in population for the countryc.
While the next Census will be based on the population as of April 1, 2020, the numbers will not be official in time to be used for that year’s presidential election. Therefore, any changes to electoral votes will be effective with the 2024 election.
(a) The 23rd Amendment (ratified 1961) granted electoral representation to the District of Columbia. The Amendment specified that DC would receive the same number of electors as if it were a state but no more than the number of electors of the least populous state.
(b) As an aside, since congressional districts are proportional to population but Senate seats are not, the net effect is that states with lower populations are over-represented in the Electoral College while those with the most population are under-represented. So California, despite having the most electoral votes, is actually the most under-represented state in each presidential election.
(c) For purposes of apportionment, the population of each state is considered to be the resident population plus overseas U.S. military and federal civilian employees (and their dependents living with them). The population of DC is not included.