In American politics, the term swing state (or battleground state) refers to any state that could reasonably be won by either the Democratic or Republican presidential candidate by a swing in votes. In 2016, the National Constitution Center listed 11 states as definite battleground states: Colorado, Florida, Iowa, Michigan, Minnesota, Nevada, New Hampshire, North Carolina, Ohio, Pennsylvania, and Virginia.  Michigan would have been more relevant to the election results had the election been closer.
Other lightly-Republican leaning states such as North Carolina and Arizona were more plausible Democratic pick-ups in 2012. - HISTORY", "A recent voting history of the 15 Battleground states - National Constitution Center", "State Electoral Vote History: 1900 to Present", "Arizona Is (Probably) Not a Swing State", "As Nation and Parties Change, Republicans Are at an Electoral College Disadvantage", "Larry J. Sabato's Crystal Ball » SENATE 2016: FLIP FLOP", "Election Update: North Carolina Is Becoming A Problem For Trump", "The Odds Of An Electoral College-Popular Vote Split Are Increasing", "Trump will be the 4th president to win the Electoral College after getting fewer votes than his opponent", "Clinton's popular vote lead surpasses 2 million", "Why FiveThirtyEight Gave Trump A Better Chance Than Almost Anyone Else", "Clinton's Leading In Exactly The States She Needs To Win", Daley Remembered as Last of the Big-City Bosses, Trolling the Campuses for Swing-State Votes, "How Dem insiders rank the 2020 contenders", "The 2020 electoral map could be the smallest in years. Michigan, New Hampshire, Nevada, North Carolina, Pennsylvania, and Wisconsin each reach this margin in three elections. Dr. Eric Ostermeier at the University of Minnesota analyzed the frequency of use for both phrases during the 2012 presidential election. , 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. With some certainty, we can narrow the field of 2020 battlegrounds to these eight states.  Both of these states have relatively few electoral votes – a total of 4 and 5, respectively.  In that election, Vice President Al Gore won the popular vote by less than 1 percent, while incoming president George W. Bush won the Electoral College by only 4 votes. Two electoral votes go to the person who wins a plurality in the state, and a candidate gets one additional electoral vote for each Congressional District in which they receive a plurality. Merriam-Webster found an example of the phrase in an 1842 edition of the Centinel of Freedom. Taegan Goddard also runs Political Wire, Political Job Hunt and the Political Dictionary.