The 2016 US presidential election is already historic, with Americans about to elect either their first female president, or their first reality television president. But it also has the potential to dramatically redraw the electoral college map.

Donald Trump, the Republican nominee, is attracting support in the so-called Rust Belt, making him a contender in Iowa and Ohio, which in recent years have been key swing states. But, early in his general election campaign, he also promised to put Democratic strongholds such as New York and California in play.

That hasn’t happened. Instead, the property developer has generated unprecedented levels of opposition from minority groups, whose rising political influence has put Republican dominance in doubt in several states, accelerating trends that the GOP establishment has long feared.

Four states in particular epitomise the Trump effect. Georgia, Arizona, Texas and Utah have not voted for a Democratic presidential candidate for at least 20 years – in Utah’s case, it has been more than half a century – but all four are poised to turn purple in 2016.

GEORGIA

Last voted for a Democrat in: 1992, Bill Clinton

RealClearPolitics polling average: Trump +4

Last week, pro-Clinton super-PAC Priorities USA Action made a $2m ad spend in Georgia, which seemed a surprising investment in a southern state that has been solidly red for the past two decades. President Obama lost the Peach State by five points in 2008 and seven points in 2012.

The last Democrat to win there was Hillary Clinton’s husband Bill, by a nose, in 1996. Yet a day after the ad spend was announced, the Atlanta Journal-Constitution released a new state poll showing that the race between Clinton and Trump was within the margin of error.

With the number of non-white voters on the rise in the region, the southeast is slowly moving towards the Democrats. North Carolina voted for Mr Obama in 2008, and is expected to fall into the Clinton column in 2016.

African-Americans comprise 30 per cent of Georgia’s electorate, and 95 per cent of them voted for Obama in 2012. Trump is haemorrhaging support among college-educated white voters in the Atlanta suburbs. If black voters turn out and college-educated white women don’t – or even decide to vote for Clinton – Georgia could swing blue as soon as November.

US election 2016: the race for the White House in pictures Show all 12 1 /12 US election 2016: the race for the White House in pictures US election 2016: the race for the White House in pictures Republican U.S. presidential nominee Donald Trump shakes hands with Democratic U.S. presidential nominee Hillary Clinton at the conclusion of their first presidential debate at Hofstra University in Hempstead, New York Reuters US election 2016: the race for the White House in pictures President Barack Obama embraces Democratic nominee Hillary Clinton on stage at the party's convention in Philadelphia US election 2016: the race for the White House in pictures Donald Trump's wife Melania delivered a speech at the GOP convention in Cleveland that was later found to have been cribbed in part from Michelle Obama's 2008 convention address AP US election 2016: the race for the White House in pictures Hillary Clinton talks to reporters aboard her new campaign plane on Labour Day, 5 September, her first 'press conference' since 2015 (Getty Images) US election 2016: the race for the White House in pictures Donald Trump held a joint press conference with Mexican leader Enrique Pena Nieto in Mexico City in August, hours before reiterating his harsh immigration plans at a campaign rally in Arizona Reuters US election 2016: the race for the White House in pictures Bernie Sanders officially endorsed Hillary Clinton, saying his progressive vision for ‘a transformed America’ would be ’best served by the defeat of Donald Trump’ Reuters US election 2016: the race for the White House in pictures Khizr and Gazala Khan appeared at the DNC to slam Trump for his stance on Muslim immigration, citing the case of their son Humayun Khan, who was killed in combat while serving as a Captain in the US Army in Iraq US election 2016: the race for the White House in pictures Libertarian candidate Gary Johnson is doing better in polls than any third party candidate since Ross Perot, 20 years ago Nicholas Kamm/AFP/Getty US election 2016: the race for the White House in pictures Green Party candidate Jill Stein (centre) marches with supporters in Colorado AP US election 2016: the race for the White House in pictures Hillary Clinton and Virginia Senator Tim Kaine at a rally in Kaine's home state in July, days before Ms Clinton tapped him to be her running mate Getty US election 2016: the race for the White House in pictures Trump on the campaign trail with his vice presidential pick, Indiana governor Mike Pence AP US election 2016: the race for the White House in pictures Former Ukip leader Nigel Farage appears at a Trump rally in Mississippi in August, where he told the crowd that he 'wouldn't vote for Hillary Clinton if you paid me'.

ARIZONA

Last voted for a Democrat in: 1996, Bill Clinton

RCP Polling average: Clinton +1.5

Arizona has voted for a Democratic presidential candidate just once since 1948. But the Clinton campaign is also making a big ad spend in the Grand Canyon State, where Michelle Obama was sent to campaign on Ms Clinton's behalf last week.

In 2012, Mitt Romney won Arizona by more than nine points. A report released afterwards by Arizona State University researchers suggested it would take until 2030 for its rising Latino population – now between 20 and 25 per cent of eligible voters – to turn the state blue.

But Trump’s anti-immigrant rhetoric has done more to mobilise Hispanic voters than any Democrat, and now the state is a toss-up in 2016. a recent poll for the Arizona Republic found that more than half the border state’s voters opposed his signature policy: a border wall.

Arizona Latino Jose Barboza talks about registering people to vote

In fact, Arizona Latino groups have been organising energetically ever since 2010, when the state’s Republican-controlled legislature passed the controversial Senate Bill 1070 (SB1070), the harshest set of anti-immigration measures anywhere in the US.

The Trump effect may also unseat another Arizona Republican stalwart. Maricopa County Sheriff Joe Arpaio, a staunch Trump surrogate, was recently charged with criminal contempt for allegedly violating a court’s order that his office desist from racially profiling Latinos.

Arpaio, who is 84 and has been in office since 1993, is running around 15 points behind his opponent.

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TEXAS

Last voted for a Democrat in: 1976, Jimmy Carter

RCP Polling average: Trump +4.8

Republicans in the Lone Star State are watching Arizona for signs of what the future may hold, as their own Latino population continues to grow. And while the demographic shift is slow, this election could prove to be an outlier, even in Texas.

In a state that Obama lost twice by more than 10 points, and where Democrats have not won a governor’s race since 1990, some polls put Clinton within the margin of error. An historic turnout of black and Latino voters could hypothetically help her to claim its 38 electoral college votes.

But while Trump was soundly beaten by Ted Cruz in the state’s Republican primary, Texans are unlikely to be broadly well-disposed to an establishment Democrat who so proudly supports gun control and abortion rights.

Texas Democrats, meanwhile, know not to get overly optimistic. Wendy Davis, a Democratic state senator who earned national headlines for her 13-hour filibuster of an anti-abortion bill in 2013, could not translate that enthusiasm into votes when she ran for governor the following year, losing to Republican Greg Abbott by more than 20 points.

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UTAH

Last voted for a Democrat in: 1964, Lyndon Johnson

RCP Polling average: Trump +5.5, with Clinton and McMullin tied

Utah, which Romney won by more than 50 points in 2012, is reliably one of the reddest states in the US. So why is Trump’s running mate, Indiana Governor Mike Pence, campaigning there this week when there are so many other battleground states that the Republicans need to win?

While Trump’s candidacy has accelerated existing anti-Republican, demographic trends in Georgia, Arizona and Texas, the threat he faces in the Beehive State is more of a freak occurrence, unique to 2016.

The property developer came in third place in the Utah Republican primary, behind Cruz and John Kasich, with a measly 14 per cent of the vote compared to Cruz’s 69.5 per cent. Two-thirds of Utah’s population is Mormon, and many of its voters are staunch conservatives.

Trump did not impress them during the primaries, particularly when he made personal attacks on his rival’s wife, Heidi Cruz. And when the Access Hollywood tape emerged, in which he bragged of having sexually assaulted women, Utah’s Republican leaders also deserted him.

The GOP nominee has been disavowed by the state’s current governor, Gary Herbert, its former governor, Jon Huntsman, and Utah Congressman Jason Chaffetz, a high-profile Clinton critic. That doesn’t mean they’re voting for Clinton, however.

Instead, many Utahans appear to be supporting a little-known independent candidate: Evan McMullin, a Republican, a Mormon and a former CIA undercover agent running as a “compassionate conservative”, who supports immigration and criminal justice reform.