Richard Nixon was born in this town, and his body lies in the grounds of a museum that contains the green army helicopter that flew him from the White House that day in August 1974 when he fled in shame.

Another GOP president, Ronald Reagan, who launched his 1984 re-election campaign nearby, cheerfully described this part of southern California as the place where “the good Republicans go to die”. The closest airport is named after John Wayne.

But Orange County is changing. Once a stronghold for conservative white Republican ideology, demographic shifts have altered the political balance. It is now one-fifth Asian, one-third Latino and a reported 45 per cent of households speak a language other than English.

Two years ago, Hillary Clinton became the first Democratic presidential candidate to win it since 1936, and in the midterms of 2018, Democrats believe they can turn Orange County blue. They are trying to do so, by fighting on kitchen table issues.

“The number one issue everyone wants to talk about is healthcare. People are afraid this administration is going to take away their healthcare,” says Gil Cisneros, 47, a former naval officer and the Democratic candidate for the 39th congressional district, which the New York Times includes among 31 “toss-ups” nationwide.

“I talked to this young mother with an eight-year-old daughter, born with a heart defect. She is worried that if they take away protections of those with pre-existing conditions, how are they going to afford for her to have more surgery. Her healthcare costs have already been more than half a million dollars. They could not have have done that without insurance … And that’s only one person.”

Orange County stretches from the warm, sun-smothered hills of Yorba Linda, to the pounding surf of Newport Beach. The county contains all, or part of, seven congressional districts. The 38th, 46th and 47th are rated solidly Democrat, but along with the 39th, the 45th, 48th and 49th are currently held by Republicans and judged toss-ups. If the Democrats bag all of Orange County it would go a long way to helping them flip the 23 seats they need to win control of the House of Representatives, the place where any attempt to impeach Donald Trump would begin.

Underscoring its importance, Democrats last month dispatched Barack Obama, where he spoke and appeared on stage with candidates from the key races. “If we don’t step up, things are going to get worse,” he said, to huge applause. “In two months we have a chance to restore some sanity to our politics.”

California Congressional candidate Gil Cisneros speaks with Andrew Buncombe

Michael Fraioli, a Washington-based Democratic strategist, says the “four targeted Orange County Republican districts are critical to Democrats winning control of the House”.

Matt Fleming, communications director for the California Republican Party, makes a similar point, from the opposite perspective. He says the party is confident about the races, and that voters have been talking about how the cost of living is too high. “Holding every seat in the state is important if we are going to have any chance of stopping the Democrats’ radical, expensive agenda,” he says .

Cisneros has gone about his task of seizing the seat in typical challenger fashion, personally engaging with as many voters as possible at their homes, at coffee shops, and meet-and-greets.

Eight years ago, he won $165m after casually buying a lottery ticket while picking up Hawaiian barbecue. He has invested much in philanthropic efforts, especially projects to help Latino youngsters. It has also presented him with a platform from which to run.

Cinseros says coming from a family of military veterans gave him a sense of service. He recently hosted military veterans for lunch at his campaign offices, where people saluted an honour guard.

“That does not change just because I got very lucky one day and became a millionaire. Because of that … is why I need to be more concerned about the direction of my country, and make sure those who do not have a voice and aren’t represented … someone is up there to speak for them.”

Republican candidate Young Kim would make history if elected (Getty)

His Republican challenger is Young Kim, an Asian-American whose candidacy underscores the changing demographics. If she wins, she would make history as the first Korean-American elected to congress.

Kim, 55, a member of the California assembly who once served as an aide to outgoing congressman Ed Royce, declined an interview request or to answer written questions. She told the Los Angeles Times she had been highlighting her experience in an immigrant family.

“My personal experience of being an immigrant, having gone through what this diverse immigrant community has gone through, struggling,” says Kim. “Those are real life experiences that really helped me understand.”

Asked how she responded to criticism of Trump’s frequent anti-immigrant rhetoric, she says: “I try to tell them I’m not running to be his spokesperson or represent Donald Trump in the White House.”

A poll taken this month by the University of California, Berkeley, showed how close the race appears to be, scoring it 49-48 in favour of Cisneros. A straw poll of potential voters in towns such as Yorba Linda, Fullerton and Placentia suggested there were lots of supporters for both candidates.

“Kim is the candidate I’ll be voting for,” says Joseph Hasrouni, a 64-year-old pharmacist who complained things were getting too hard for the middle class, but who believed Republicans would better address the problem. “I like their way of thinking. I am conservative.”

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Majid Fadaee, 62, says for him the most important issue was protecting the environment – an issue on which Trump has been strongly condemned. He said he would vote Democrat. “The Democrats always do a better job for the environment.”

Of the other too-close-to-call races in Orange County, another receiving much attention and large amounts of money is the 48th, which pitches Democratic challenger Harley Rouda against 15-term Republican incumbent Dana Rohrabacher. Though he was not accused of any crime, the Republican was last month named in court papers that alleged Trump’s former campaign Paul Manafort, had in 2013 tried to lobby him on behalf of the pro-Russian former president of Ukraine, Viktor Yanukovych. Rohrabacher has often defended Vladimir Putin and dismissed the assertion by US intelligence that Moscow interfered in the 2016 election.

Rohrabacher has also been in the headlines over the years for denying climate change. More recently he defended people who to refused to sell their homes to gay people, and was duped by Sacha Baron Cohen in supporting a fake gun-training programme for toddlers.

On a recent sunny evening in the hillside community of Laguna Niguel, a team of volunteers for Rouda set off knocking on doors, adamant 71-year-old Rohrabacher should not get a 16th term.

Jeff Johnson, one of the organisers, says when he first met Rouda he seemed well informed on issues of most concern to people – healthcare and the economy. He says enthusiasm among the volunteers is high, and teams have been canvassing or operating phone banks in Laguna Niguel at least four days a week.

Democratic candidate Gil Cisneros, a former naval officer who ‘got lucky’ (Getty)

Johnson, a retired furniture designer, says such engagement could make all the difference. In the open primary held in July, which Rohrabacher won handily, Rouda snuck into second place to get the chance to contest the Republican, by just 125 ballots. He says: “Every vote counts.”

The race in the 48th is as close as the contest between Cisneros and Kim.

A poll published by the Los Angeles Times tied the two men on 48 points. It also said 10 per cent of registered Republicans and 45 per cent of undecided voters were less likely to vote for Rohrabacher after talk of his alleged Russian ties – which he denies – made the news.

Rouda says two issues keep coming up when meets people – the cost of healthcare coverage and a desire for a representative who connected with people. He claims his rival has barely ever met with his constituents.

In a telephone interview, he defends the decision to target disillusioned conservatives.

The army helicopter that flew Richard Nixon from the White House following his 1974 resignation (Getty)

“Forget whether the word Democrat is next to a person’s name – see if that person’s values match yours,” he says of his message. “[Rohrabacher] has been here 30 years and he has been one of the worst records for getting tax dollars spent here.”

Asked how he hoped to defeat someone who won more than 50 per cent of all votes in this summer’s primary, he says: “Working hard, being committed to the people of the 48th and district and being accountable.”

Rohrabacher’s office failed to respond to requests for an interview.

In a recent debate with Rouda recorded for Inside OC, Rohrabacher accused his challenger of being weak on immigration.

“We’ve had 30 million illegals crossing into our country in over the last 20, 30 years. If we ignore that, number one, it’s draining the money from all these programmes we’re talking about. When you talk about giving medicare to illegal immigrants, you’re going to collapse that system,” he said.

Rouda says he supports providing healthcare for undocumented adult immigrants. “Let me be very clear. Representative Rohrabacher wants to deport everyone who is here undocumented. And he wants to charge them … a million dollars each to come back to build the wall.”

Rohrabacher, who has teenage triplets, describes himself as keen surfer and has used photographs of himself in a wetsuit for his campaign.

Yet on an evening walk along Huntington Beach, long celebrated as one of the country’s favoured surfing spots, it is not easy to find supporters of the congressman.

Laura Hiller, who usually votes Republican, says she will be casting her ballot for John Cox, the GOP candidate for California governor.