Normally, a Republican congressman in a ruby red district has little to worry about come re-election time.

But Rep. Duncan Hunter, R-Alpine, who represents most of Temecula, finds himself on the Democrats’ 2018 target list — in no small part due to the ongoing federal investigation into his campaign spending.

“Congressman Duncan Hunter has a long record of repeatedly neglecting his constituents for personal gain, leading to an unprecedented FBI investigation into a possible cover-up of illegal campaign spending,” said Drew Godinich, a spokesman for the Democratic Congressional Campaign Committee.

“That, along with a deep bench of tough Democratic challengers, has made this seat vulnerable in 2018.”

Hunter did not respond to a request for comment.

At least five candidates, including a Republican, are running to unseat Hunter, who represents California’s 50th Congressional District, which covers much of San Diego County and about two-thirds of Temecula.

The Democratic Congressional Campaign Committee and its GOP counterpart, the National Republican Congressional Committee, tend to focus on open seats and districts represented by vulnerable incumbents in the other party.

Hunter’s district fits neither category. In a state where Democrats dominate, 43 percent of district voters are registered Republicans as of February compared to 27 percent for Democrats, numbers from the Riverside and San Diego registrars of voters show.

No Democratic candidate has ever won more than 40 percent of the district’s vote, although Hillary Clinton got 39.56 percent in November, said Rob Pyers, research director for the nonpartisan California Target Book, which analyzes state races.

Hunter, 40, succeeded his father, also named Duncan Hunter, who was a GOP congressman from 1981 to 2009.

Since being elected to the only public office he’s ever held, the junior Hunter, who was the first Marine combat veteran of Iraq and Afghanistan to serve in Congress, has earned a reputation as an outspoken politician. He became known as “the Vaping Congressman” after he vaped during congressional hearings on proposals to ban vaping on airliners.

Hunter was one of the first congressmen to endorse then-presidential candidate Donald Trump. At a Riverside County Young Republicans meeting in Murrieta in August, he reportedly called Trump “an (expletive). But he’s our (expletive).”

Riverside County GOP Chairman Jonathan Ingram, who was at the meeting, said Hunter was joking, and his remarks were taken out of context. Hunter still has strong support among local Republicans, said Ingram, a Murrieta councilman who described himself as a personal friend of Hunter’s.

Campaign expenses

Hunter’s legal headaches started in 2016 when The San Diego Union-Tribune reported on $1,300 in online video game purchases charged to his campaign account. At the time, Hunter, a married father of three, said his son used a campaign credit card to buy the games.

Other reports of questionable spending followed, including campaign payments to his kids’ private school, an oral and facial surgeon, fast food, groceries and costs tied to trips to Italy and Hawaii. The campaign’s credit card was even charged $600 to fly the Hunter family’s pet rabbit; Hunter spokesman Joe Kasper described the charge as an oversight and brought it up in the context of criticism of the Office of Congressional Ethics.

Hunter eventually ordered an outside audit and reimbursed his campaign $60,000. He took responsibility for the charges, saying they were not intentional. He said he’s taken steps to prevent similar expenses from being charged in the future.

In March, the House Ethics Committee announced it would defer its probe into Hunter’s campaign spending at the request of the Department of Justice, which was conducting its own investigation. FBI agents got a warrant to search the workplace of Hunter’s campaign treasurer in February and came away with computers and documents, according to published reports.

Hunter maintained his innocence in a March interview with POLITICO.

“I was not involved in any criminal action,” he was quoted as saying. “Maybe I wasn’t attentive enough to my campaign. That’s not a crime.”

Kasper, who serves as Hunter’s chief of staff and worked for the congressman’s father, announced earlier this month he was leaving. He said his departure had nothing to do with the investigation.

The probe appears to have stunted Hunter’s political fundraising. Pyers of the Target Book, described Hunter’s fundraising as “atrocious,” Almost $153,000 of the roughly $156,000 Hunter raised from April 9 to June 30 went to legal fees, which come out to more than $336,000 so far this year, Pyers said.

By comparison, one of Hunter’s Democratic opponents, Ammar Campa-Najjar, raised more than $165,000 in the second quarter, while another Democratic candidate, Josh Butner, raised roughly $141,000 from April 9 to June 30, according to the Federal Election Commission website.

Others challenging Hunter include Patrick Malloy, a Democrat who lost to Hunter in 2016, Democrat Pierre Beauregard and Republican Andrew Zelt. The top two vote-getters in the June 2018 primary, regardless of party, will advance to the November general election.

“Badge of honor”

Despite Hunter’s troubles, Pyers said Democrats face tough odds in flipping the 50th District.

Assuming the Democratic field stays packed, and the candidates splinter a small piece of the voting pie among themselves, Hunter and Zelt, the other Republican, could make it out of the primary, he said.

“If Hunter is facing a non-baggage laden Republican opponent in November and he continues to be under an ethical cloud, it has the potential to be a competitive race,” Pyers said. “If he’s facing a Democrat in November, ethical cloud or not, his chances are greatly improved.”

Jennifer Walsh, a political science professor and dean of the College of Liberal Arts and Sciences at Azusa Pacific University, agrees that Democrats are fighting uphill battle to unseat Hunter, who won re-election in November with 64 percent of the vote.

“They either have to field both of the top two vote-winners in the primary, which would be next to impossible in a district that is heavily Republican, or they have to convince voters who normally vote Republican to abandon their party allegiance and vote Democrat in the general election,” she said.

“Even if the Democrats field a more-conservative candidate in an attempt to woo Republican voters, a Democratic win seems implausible.”

Hunter’s recent Trump remarks and the FBI investigation might energize Hunter’s base, Walsh added.

“His profanity-laced praise of President Trump resonated well with his core supporters, many of whom embrace Trump for his candid and politically incorrect comments,” she said. “In addition, his active investigation by the FBI could be interpreted as a badge of honor, as federal law enforcement forces are often thought of in politicized terms by President Trump supporters.”