The following is a listing of American states based on their respective success rates at picking the winning president (since 1960). The leaders are Nevada and Ohio at 87.5%, making them true battleground / swing states in any given election. As swing states go, Arizona is the poorest performer at 56.3%. The poorest overall rate is held by the District of Columbia (D.C.) with a success rate of just 43.8% (namely due to the fact that it tends to vote strictly along the Democratic Party line). The top ranking Democratic and Republican states are Delware and New Mexico / Missouri, respectively, these having a success rate of 81.3%.
In the listing below, Red states are those typically leaning Republican while Blue represent Democratic leaners. Black states are those considered 'Battleground' or 'Swing States' in any given presidential election cycle.