what are the swing states
From recent past electoral results, a Republican candidate can expect 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, Georgia, Mississippi, Louisiana, Arkansas, Tennessee and South Carolina, as well as Alaska. A Democrat usually takes the Mid-Atlantic states, including New York, New Jersey, Maryland and Delaware, along with New England, particularly Vermont, Massachusetts, Rhode Island, and Connecticut, the West Coast states of California, Oregon and Washington, along with Hawaii.
The electoral college encourages political campaigners to focus on these swing states while ignoring the rest of the country. States in which polling shows no clear favorite are usually inundated with campaign visits, television advertising, get-out-the-vote efforts by party organizers and debates, while “four out of five” voters in the national election are “absolutely ignored,” according to one assessment. 
The term swing state is used in two different ways.
Swing states are also sometimes referred to as battleground states. More than a dozen states are considered swing states, and most of them hold a large number of electoral votes and are considered major prizes in presidential elections.
With that feat, Trump shattered the presidential map we’ve grown accustomed to. The most immediate consequence was to blow up the idea of a “Blue Wall,” a term applied to a northern tier of 18 states, stretching from coast to coast, that appeared to provide a structural advantage for a Democratic nominee. Going into the election, it seemed almost unbreachable, which was a key factor driving the belief that Hillary Clinton was on a glide path to the presidency.
Ohio, a traditional Midwestern bellwether, epitomized the old electoral map, from the now-distant era when presidential elections featured dozens of contested states and candidates sought to campaign in all of them. Virginia, a Southern state that for decades had voted Republican for president until Obama broke the streak in 2008, represented a new map, one in which rapid demographic change created new opportunities for Democrats. Together, they were emblematic of the Electoral College map Obama and his diverse coalition rewired in 2008 to win the White House.
As former Clinton political director Doug Sosnik told Axios just after the 2018 elections: “Changing demographics and Trump have blown up the electoral map that has dominated American politics since 1992.”
He notes that the midterm elections also showed “that without Hillary atop the ticket, Midwest states like Wisconsin are tough for Trump, and Southern states with rising Hispanic populations are slowly growing more Democratic.”
What’s it looking like for the 2008 election? Washington Post political blogger Chris Cillizza lists Iowa, New Mexico, Nevada, Colorado, Ohio, Virginia, New Hampshire, Florida, Minnesota and Missouri as potential swing states in the 2008 election [source: Washington Post.com].
Sometimes states are considered swing states for reasons beyond close margins. For example, for the 2004 election West Virginia, Louisiana, Arkansas and North Carolina (because it is the home state of Senator John Edwards, who was Kerry’s running mate in 2004) were also considered swing states by political analysts.