The freedom to change voting policies and systems at the state level, however, is why you see proportional distribution of electoral college votes in some states, for example. (politics.stackexchange.com)
Therefore, a candidate could win a single electoral college vote by winning one district in either state. (politics.stackexchange.com)
Figure 6: Number of electoral college votes won by Republican presidential election candidate by region, 1972 - 2016 (adriankavanaghelections.org)