Swing state

In past electoral results, Republican candidates would have expected to easily win most of the mountain states and Great Plains, such as Idaho, Wyoming, the Dakotas, Montana, Utah, Kansas, Oklahoma, and Nebraska, most of the South, including Alabama, Mississippi, Louisiana, Arkansas, Tennessee, Kentucky, South Carolina, Missouri, Texas, and West Virginia, as well as Alaska.

A campaign strategy centered on them, however, would not have been meaningful in the Electoral College, as Democratic nominee Walter Mondale required victories in many more states than Massachusetts, and Republican Ronald Reagan still would have won by a large margin.

Similarly, Barack Obama's narrow victory in Indiana in the 2008 election inaccurately portrays its status as a battleground.

[17][18] This meant that Donald Trump would have picked up New Hampshire, Nevada, and Minnesota if the popular vote had been tied, assuming a uniform shift among the battleground states.

This shows Donald Trump could win the election even if he lost the popular vote by over 3 percent and would have picked up Georgia, Arizona, and Wisconsin with a uniform shift among the states.

This is evidence of an erosion of the popular vote advantage that Democratic candidates have typically enjoyed in recent elections, likely spurred by a significant narrowing of margins in safe blue states such as New York, New Jersey, and Illinois, which each saw dramatic shifts toward the Republican candidate, as well as dramatic increases in the Republican support in moderately red states such as Florida and Texas compared to previous cycles.

For instance, the swing states of Ohio, Connecticut, Indiana, New Jersey and New York were key to the outcome of the 1888 election.

[27][28] In fact, only three people have won the presidential election without winning Ohio since 1900: Franklin D. Roosevelt, John F. Kennedy, and Joe Biden.

Areas considered battlegrounds in the 2020 election were Arizona, Florida, Georgia,[29] Iowa, Maine's 2nd congressional district, Michigan, Minnesota, Nebraska's 2nd congressional district, Nevada, New Hampshire, North Carolina, Ohio, Pennsylvania, Texas and Wisconsin,[30] with Florida, Michigan, Ohio, Pennsylvania, and Wisconsin constituting the "Big Five" most likely to decide the Electoral College.

For example, in the 2016 election, Hillary Clinton overperformed in educated, suburban states such as Colorado and Virginia compared to past Democratic candidates, while Donald Trump performed above standard Republican expectations in the Rust Belt, such as Michigan, Ohio, Pennsylvania, and Wisconsin.

In addition, gradual shifts can occur within states due to changes in demography, geography, or population patterns.

[33] According to a pre-election 2016 analysis, the thirteen most competitive states were Wisconsin, Pennsylvania, New Hampshire, Minnesota, Arizona, Georgia, Virginia, Florida, Michigan, Nevada, Colorado, North Carolina, and Maine.

[37][38][39] The Electoral College encourages political campaigners to focus most of their efforts on courting voters in swing states.

States in which polling shows no clear favorite are usually targeted at a higher rate with campaign visits, television advertising, and get out the vote efforts by party organizers and debates.

In contrast, many states with large populations such as California, Texas and New York have in recent elections been considered "safe" for a particular party, and therefore not a priority for campaign visits and money.

[41] Additionally, campaigns stopped mounting nationwide electoral efforts in the last few months near/at the ends of the blowout 2008 election, but rather targeted only a handful of battlegrounds.

This takes into account inherent electoral college advantages; for example, Michigan was the closest state in 2016 by result, and Nevada was the closest state to the national popular vote result, but the tipping points that most mattered for assembling a 270 electoral vote coalition were Wisconsin and Pennsylvania.