SAN DIEGO (AP) — A fierce fight between Republican candidates has punctuated the race for the vacated seat of disgraced California GOP Rep. Duncan Hunter, who dropped out and resigned from Congress in January after pleading guilty to a corruption charge.

The 50th District east of San Diego is among the last Republican strongholds in Southern California. The GOP front-runners are San Diego radio host and political commentator Carl DeMaio and former U.S. Rep. Darrell Issa, who retired from a neighboring district in 2018.

During a nasty primary campaign, they have questioned each other's allegiance to President Donald Trump and accused the other of lying about their records.

Under California election rules, the top two vote-getters in Tuesday's primary advance to the general election, regardless of party affiliation. While it's possible that could be Issa and DeMaio it's far more likely one is eliminated and the other faces off against the only Democrat in the field, 31-year-old former Obama administration official Ammar Campa-Najjar.

Campa-Najjar narrowly lost in 2018 to Hunter, who ran while under indictment on corruption charges. Hunter faces sentencing later this month.

Holding the district is critical for Republicans. who have just six of 53 House seats in California. The 50th, a swath of suburbs and farm towns in eastern San Diego County that runs into the wine country of Riverside County, is one of Southern California's last conservative strongholds. Registered Republican voters there hold an 11-percentage point edge over Democrats.

It's been an expensive battle for the top Republicans. Issa, 66, a car alarm magnate and one of the wealthiest lawmakers when he served, has spent about $2.7 million. DeMaio, 45, a former San Diego city councilman, has spent about $2 million. A third GOP candidate expected to siphon away some Republican votes is state Sen. Brian Jones.

The San Diego Union-Tribune, the largest local newspaper, endorsed Jones and Camp-Najjar, saying of Issa and DeMaio that a "general election without this pair’s vitriol would be a blessing.“ Neither actually lives in the district, a point Jones has sought to drive home.

Issa built a national reputation and a became favorite within the GOP when he chaired the House Oversight and Government Reform Committee and served as the chief congressional antagonist to then-President Barack Obama. After narrowly winning reelection in 2016, Issa decided not to run again two years later in the 49th District where Democrats had been gaining ground for years.

Issa and DeMaio share similar agendas that support Trump's stands on issues such as stricter immigration enforcement and gun rights. But each has tried to make voters believe the other is not truly in step with the president, who has not endorsed either candidate.

Issa faced backlash even from Republican supporters for an advertisement that included references to headlines noting the sexual orientation of DeMaio, who is gay. Critics said it amounted to gay-baiting. Issa defended it, saying media outlets wrote the headlines and the ad was meant to highlight DeMaio's record.

Campa-Najjar has also touted his local roots, Christian faith and gun ownership to woo independents and moderate Republicans. He is pro-choice but says he will not blindly follow Democrats on all issues. For instances, he said he wants new versions of the proposed medicare-for-all and the Green New Deal, a package of legislation to address climate change, that both parties could support.

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This version corrects in the 4th paragraph the spelling of the last name of the candidate who is a political commentator. DeMaio, not DaMaio.