Duncan Hunter's re-election campaign in California’s 50th district was once considered a relatively easy victory.

Then, along came a slate of scandals — and Ammar Campa-Najjar.

As the Republican congressman’s lead continues to slip amid new controversies, his opponent — the first Latino-Arab American to run for Congress — has seen a surge in support for his progressive campaign, telling The Independent in a recent interview, "I think I’ve risen to the occasion and I believe the voters will too."

Mr Hunter's incumbency came under threat when he and his wife were indicted by a federal grand jury in August on charges alleging the two used upwards of $250,000 in campaign funds towards tequila, golfing and vacations, among other personal expenses.

Mr Hunter has denied the charges, telling Fox News: “I didn’t do it. I didn’t spend any money illegally.”

As the congressman’s opponent began to close in on his lead, with the latest surveys showing Mr Campa-Najjar within the margin of error, Mr Hunter has sharpened his rhetoric against the Democrat.

“Radical Muslims are trying to infiltrate the US government,” Mr Hunter said at a recent campaign event. “You had more Islamists run for office this year at the federal level than ever before in US history.”

To be clear, Mr Campa-Najjar is a Protestant — he grew up in a Christian home and joined a youth ministry at 16-years-old, according to a statement his pastor released — but that has not stopped Mr Hunter from releasing a slew of Muslim-shaming attacks.

Last week, his campaign released an advertisement claiming Mr Campa-Najjar was supported by the Muslim Brotherhood and suggested he had changed his name to conceal his Muslim-linked identity.

However, the Washington Post reported earlier this year the 29-year-old changed his last name in 2016 “in honuor of his mother’s family, the Campas, who helped raise him.”

Mr Campa-Najjar tells The Independent he isn’t concerned about the attacks against him derailing his campaign.

“Despite paid media and a couple hit jobs, it didn’t work: I was still able to win the primary,” he said. “So I’m not concerned about it. I think I’ve risen to the occasion and I believe the voters will too … there are people banking on the fact that voters will be conned into thinking any of this matters”.

His campaign has gained six per cent in the polls over the last two months in his battle against Mr Hunter, who maintains a lead with 48 per cent of support from voters across the district, according to a survey conducted by SurveyUSA for the San Diego Union-Tribune between 25 October to 29 October.

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He’s within spitting distance of unseating the Republican incumbent — just like a slew of other progressive candidates threatening Republican strongholds, from Beto O’Rourke in Texas to Stacey Abrams in Georgia — as the margin of error for the survey is plus or minus 4.8 per cent.

However, it remains unclear what scandals may ultimately determine the fate of the race: the very real ones facing Mr Hunter, or the grossly-inflated “controversies” surrounding Mr Campa-Najjar.

Several right-wing outlets have pointed to the fact that the Democrat’s grandfather was one of the notorious terrorists involved in the 1972 Munich terror attack.

Mr Campa-Najjar has never met his grandfather, who died 16 years before his birth, and says the issue “plays on xenophobia and distorting facts, and it really has no bearing.”

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“This is another ploy from out-of-touch forces, who play identity politics and don’t want to talk about the issues,” the candidate said. “Obviously, people make a lot of assumptions about me that are not accurate.”

He added, “When it comes to my distant relative — who died 16 years before I was born — he influenced my thinking as much as he did yours, which is not at all.”