How Swing States Work
What exactly are swing states?
Swing states (also known as "purple" or "battleground" states) are those states where the popular vote is usually a very close call and as such become extremely important, if not crucial, to the outcome of the presidential election. Swing states can also vary by election years depending on changing demographics.
How swing states are different from regular voting states
States designated as regular voting states are those that tend to vote primarily along party lines in each election. Traditionally a higher number of regular states have shown strongest affiliation with the Republican nominee. Swing states, on the other hand, are those that have decided the presidential election by a narrow gap, as was the case in 2000. In addition, a candidate's home state may also turn from a regular state to a swing state for the sole reason that the candidate is considered a favorite.
States that are neither swing nor regular
The states of Nebraska and Maine follow a "district" system, rather than the customary Electoral College (https://www.avvo.com/legal-guides/how-electoral-college-works) method. In both of those states, two electors' votes are made in accordance with the number of votes in the state for each candidate. Then, veering from the standardized practice, the rest of each state's electoral votes are awarded by its various congressional districts, which vote in accordance with whoever was given the most votes in their particular district.
Why swing states are so important
Swing states, particularly those with a large number of electors, can often make or break an election. Therefore, presidential candidates and their constituents tend to "court" voters and plan their campaign strategy around those states where the margin of votes tends to be extremely close. These are the places where it is a common to see candidates shaking hands in a crowd, being photographed with potential voters, making heartfelt speeches, and heavily promoting themselves on television spots. This is not to say that candidates ignore the regular states. On the contrary, regular states are those that tend to promote fundraising events to keep the campaign money flowing for their candidates.
How swing states and the Electoral College affect one another
Although it may seem that the popular vote (where voters make the ultimate decision) is the fairest way to decide a presidential election, this is not how the United States system works. The Electoral College mandates the outcome (https://www.avvo.com/legal-guides/how-electoral-college-works). The majority of electoral votes required to elect the president is 270, and the current number of electors is 538. A Democrat who lives in a regular state that overwhelmingly votes Republican can likely assume that the elector for that state will vote Republican. In swing states, however, voting margins are extremely close: often less than one percent. One good example of the impact of swing states is the historic 2000 presidential election, in which the outcome of that highly and hotly disputed contest had the country (and the world) focused on Florida and just 537 votes that were cast by 25 electors. This scant 0.01 percent margin decided the presidential election. Florida, almost a balance of Democratic and Republican bastions, has since added two electors.