Share of electoral votes for major parties in US presidential elections 1860-2020

With Abraham Lincoln's victory in the 1860 presidential election, the Republican Party cemented their position as one of the two major political parties in the United States. Since 1860, candidates from both parties have faced one another in 41 elections, with the Republican candidate winning 24 elections, to the Democrats' 17. In the U.S., the electoral college system is used to elect the president; for most states, this means that the most popular candidate in each state then receives that state's allocation of electoral votes (which is determined by the state's population). In the majority of elections, the margin of electoral votes has been over thirty percent between the two major party candidates, and there were even some cases where the winner received over ninety percent more electoral votes than the runner-up.
The largest margins for the Republican Party occurred in the aftermath of the American Civil War, in the inter-war period, after the Second World War, and then again with the Nixon, Reagan and George H. W. Bush campaigns in the 1970s and 80s. For the Democratic Party, the largest victories occurred during First and Second World Wars, and for Lindon B. Johnson and Bill Clinton in the second half of the twentieth century. In the past six elections, the results of the electoral college vote have been relatively close, compared with the preceding hundred years; George W. Bush's victories were by less than seven percent, Obama's victories were larger (by around thirty percent), and in the most recent elections involving Donald Trump he both won and lost by roughly 14 percent. The percentage of electoral college votes are often very different to the percentage of the popular vote received by each candidate in the elections, as the popular vote differences tend to be much smaller.