There may be 50 states in the United States of America, but every four years the election of a new president rests on the contests in about a dozen states: the election battlegrounds.
Most states consistently back one party. Southern states such as Alabama and Mississippi are considered guaranteed Republican wins, while California and Massachusetts regularly vote Democratic.
If you track the visits by the two main-party candidates, you will see the airplanes of Donald Trump and Hillary Clinton regularly heading to the electoral front lines: Florida, Ohio, North Carolina, New Hampshire, Pennsylvania, Iowa, Nevada, Colorado and Maine.
The blustering rhetoric and polarising proposals of Trump have made states that have traditionally voted Republican for two decades such as Arizona and Georgia competitive races again, opening a "New South" or "South West" strategy for Democratic nominee Clinton. Demographic changes with growing minority communities have pushed one-time swing states such as Virginia and Colorado closer to the Democratic Party.
Clinton’s advantage in the electoral college, with large support in the heavily populated states on the coasts such as California and New York, gives her a head-start in the race to the 270-vote majority in the electoral college. This makes Florida, the biggest swing state with 29 electoral votes, Ohio with 18 and North Carolina with 15, must-win battlegrounds for Trump.
He has marked out Pennsylvania, a Democratic state where he has campaigned heavily over the past year, particularly in the west of the state, as a key target. It is part of his Rust Belt strategy to win over record numbers of economically frustrated blue-collar white voters with his promise to rebuild the American manufacturing sector and bring jobs back lost to low-cost countries.
The New York businessman’s poor rating among African-American, Hispanics and other minority voters leaves him requiring the support of white voters at a level not seen since Ronald Reagan’s 49-state landslide re-election in 1984, when he won 66 per cent of the white vote, and hoping that a lack of enthusiasm for Clinton among Democrats will depress her turnout.
His divisiveness has hurt him among one key Republican constituency: white voters with a college degree. No Republican has lost this group since 1956. This gives Clinton an edge in North Carolina, Virginia and Colorado, which has a significant proportion of college-educate voters.
Trump is counting on bucking a long-term trend. He has to mobilise white voters without college degrees – a group that has tended to stay at home in previous elections – in large numbers that he will offset losses among college-educated whites, particularly women, and minority voters, delivering him victories in Rust Belt states in the American midwest and mid-Atlantic region.
The election will be decided not by working-class whites but by suburban upper-middle-class white voters and whether they will vote or sit out this a contest of two unpopular candidates.
THE BATTLEGROUNDS
[ Florida (29 electoral votes)Opens in new window ]
Donald Trump has no realistic chance of winning the White House without Florida, the largest swing state in the country. Clinton's massive lead among black, Hispanic and other minority voters – who made up a third of the state's voters in the 2012 election – is offset by Trump's strong support among white working-class voters angry with Washington politics and stagnant wages. The huge influx of Puerto Ricans, US citizens who like to vote, and Latino immigrants into the Orlando area and the pivotal I-4 corridor (named after the inter-state running between Orlando and Tampa that bisects central Florida) will help Clinton's chances in the state.
[ Ohio (18 electoral votes)Opens in new window ]
No Republican has won the White House without the state of Ohio and the midwestern state has swung for every successful candidate since 1964, making it a bellwether for the election. The Rust Belt state’s large population of blue-collar whites in the east and the Appalachian southeast may help Trump outperform Mitt Romney’s effort among these voters in 2012. The Republican nominee’s tough anti-trade, anti-immigration talk appeals to people in the downtrodden coal and steel towns, but Clinton has strong support in the Democratic strongholds around Cleveland and Columbus. She may be helped too by the college graduates and moderate Republicans in the suburbs turned off by Trump’s incendiary language and alleged sexual misconduct with women.
[ North Carolina (15 electoral votes)Opens in new window ]
Trump needs to retain this purple state (won by Republicans in 2012 but lost in 2008) to help close the Democratic electoral advantage. The large non-white population (about 29 per cent of the state) and significant numbers of white college graduates around the major cities will favour Clinton but this is a conservative state so it will be close. A more effective Democratic grassroots organisation and early-voting drives may give Clinton an edge.
[ Pennsylvania (20 electoral votes)Opens in new window ]
Democratic strategist James Carville jokes that Pennsylvania is Pittsburgh and Philadelphia "with Alabama in between." Trump's "America First" jobs pledge is popular with many in the declining coal-mining and steel-milling towns in the "in-between" parts of western and central Pennsylvania. But the businessman will have to get out these voters in big numbers – and sustain the traditional Republican support in suburban areas (where he is struggling) – to offset Clinton's support in the two big cities if he is to become the first Republican to win here since 1988.
Iowa (6 electoral votes)
The state has voted Democrat in six of the last seven presidential elections and twice for Obama. The state has a whiter and less educated population than other swing states, giving Trump an advantage. Clinton has struggled here in her primaries, coming third in 2008 and eking out a tiny win over Bernie Sanders this year. Winning over 36 per cent of registered voters who do not affiliate themselves with any party will determine who wins this state.
[ Nevada (6 electoral votes)Opens in new window ]
Bill Clinton, George W Bush and Barack Obama each won Nevada twice, so it's as purple as battlegrounds come. Nevada has the second-largest Hispanic population of the swing states (behind Arizona and ahead of Florida) but a less educated population – just 22 per cent of the population are college graduates – netting off gains for both candidates. High unemployment in the state puts another thumb on the scale for Trump.
[ New Hampshire (4 electoral votes)Opens in new window ]
The Granite State voted Republican in the six presidential elections between 1968 and 1988 but went Democratic in five of the last six. The state is fiscally conservative but socially liberal, leaving Republicans in the state increasingly at odds with their own party. Trump is a regular visitor to the state that handed him his first primary victory and he has identified New Hampshire as a target primarily because of its independent streak; the state had the second-largest share of self-professed independents – 43 per cent voters – in the country in 2012, according to exit polls. The state’s mostly white voter base has less potential for the Trump Factor because it is more educated. The state has the fourth-largest percentage of white voters with at least a college-degree in the country. The Clinton camp’s biggest concern about New Hampshire is that younger Democrats who picked Sanders over her in the party’s primary might sit it out the election.
[ Arizona (11 electoral votes)Opens in new window ]
The last two Democrats to win Arizona were Bill Clinton in 1996 and Harry Truman in 1948 so this should be a deeply crimson state. But the state's population is growing fast and diversifying. Trump's hardline stance on illegal immigrants has alienated many Hispanics who make up almost a third of Arizona's population. The Clinton camp is eyeing an opportunity in this southwestern border state and has applied more resources to the state and sent surrogates to rally the vote. The state is home to more than 400,000 Mormons, a stead-fast conservative voting bloc who may be loathe to embrace Trump and prefer the independent conservative Evan McMullin, a Mormon. Trump still enjoys plenty of support among the state's anti-immigration conservatives.
[ Georgia (16 electoral votes)Opens in new window ]
This year's unconventional match-up between two disliked candidates has the potential to redraw the electoral map and Georgia, like Arizona, could see significant changes. This southern state only voted Democratic three times since 1964 – for home-boy Jimmy Carter twice, in 1976 and 1980, and Bill Clinton in 1992. The state has become much more diverse since Romney won here in 2012 and Clinton benefits from Trump's poor support among black Georgians who make up 32 per cent of the population, and other minorities moving into the expanding Atlanta metropolitan area. Her advantage among college-educated voters will also help.
Virginia (13 electoral votes)
This state most reflects the changing demographics favouring the Democrats. It was a Republican stronghold until 2008 when Barack Obama became the first Democrat to win Virginia in 44 years. A large black population (20 per cent of residents) along with growing immigrant communities and large numbers of college graduates in northern Virginia, including in the suburbs of neighbouring Washington DC, makes this difficult electoral territory for Trump.
Colorado (9 electoral votes)
Obama won Colorado in 2008 and 2012 but before him the Centennial State swung Republican in the three previous elections. An increasing number of younger voters, urban residents, more diverse voters and educated moderates means Colorado has trended left with registered Democrats growing in numbers. The state has strong conservative pockets, for example around Colorado Springs, and an independent streak that will push the support for third-party candidate, the Libertarian nominee Gary Johnson. Some 43 per cent of Colorado residents have a university degree, leaving Trump with an uphill climb in this Rocky Mountain state.
Wisconsin (10 electoral votes)
Democrats have not lost Wisconsin since Ronald Reagan's 1984 landslide, thanks in recent elections to their support in Milwaukee and Madison. The Badger State has a large white population and has a lower number of college graduates than other battlegrounds, but Trump is struggling in the state's most populous counties in southeastern Wisconsin around the Milwaukee suburbs. He lost the Republican primary here after a strong Never Trump movement led by conservative radio hosts. His raging battle with Wisconsin's Paul Ryan, the Republican Speaker of the House of Representatives who refuses to defend him, does not help his chances.
Michigan (16 electoral votes)
This state shows the weakness in Trump’s Rust Belt plan of attack. The industrial midwestern state that relied heavily on manufacturing and steel jobs should be a place where his message does well but one in five Michigan residents are non-white, creating a demographic that will make it hard for Trump to become the first Republican to win this state since 1988.