Hunter faced significant odds of winning the two-third support he needed for the nod from the San Diego Republican Party, with several other GOP candidates dividing the vote, including former Rep. Darrell Issa. But it's nonetheless an unwelcome result for a campaign widely seen as vulnerable.
In remarks at a party forum in San Diego that were at turns fiery and defiant, the Southern California congressman suggested his rival candidates should look elsewhere for political opportunities.
"I've got this seat," Hunter said, with three other candidates seated beside him.
"I've won this seat in the worst of times. I'm still fighting from this seat. I'm still fighting for you," he said.
The party did not release the vote tallies for each candidate.
The federal charges against the 42-year-old lawmaker came up only glancingly throughout the hour-long forum, but they are an overarching issue in a contest in which the Republican candidates largely agree on immigration, opposition to abortion, defense of the Second Amendment and support for President Donald Trump.
His trial is scheduled to begin in January. Hunter and his wife were charged with misspending more than $200,000 in campaign funds on vacations, bar tabs and other personal expenses.
Margaret Hunter, who served as the congressman's campaign chairwoman, later pleaded guilty to one count of corruption and agreed to testify against her husband. Prosecutors have also charged that Duncan Hunter used campaign money to finance romantic flings with lobbyists and congressional aides.
Hunter has pleaded not guilty and has called the charges a politically motivated attempt to drive him from office.
Hunter referred to the charges in his initial statement at the forum, while appearing to depict Issa and radio personality Carl DeMaio as interlopers unfamiliar with his district.
Hunter noted that he carried the Republican-leaning 50th District in 2018 even after being charged, in a year when Democrats seized a string of Republican-held congressional seats in the state in a rout.
"I'm not going to move somewhere and fight for the easy seat," Hunter said in what appeared to be another dig at his challengers.
"Even when Democrat operatives in a U.S. Attorney's Office indicted me months before my election, tried to steal my seat, I still won," he said.
Issa, DeMaio and state Sen. Brian Jones steered away from direct attacks on Hunter, whose father held the seat in Congress before him.
Issa, who was known as one of President Barack Obama's chief antagonists in Congress, appeared to hint at Hunter's legal problems indirectly, at one point asking, "Do you have someone who arrives able to lead on day one?"
Republicans have a voter registration advantage in the 50th District, which covers east San Diego County and a small part of southern Riverside County.
The district represents something of a Republican outpost in a state where Democrats dominate statewide politics. Hunter narrowly survived a 2018 challenge, when Democrat Ammar Campa-Najjar came within 3.4 percentage points of winning the seat in his first run for Congress.
Hunter depicted himself as more than capable of holding the seat and doing his job in Washington, despite his legal troubles.
The combat veteran said, "As a United States Marine, what we do is we stand up and we fight. And we fight."
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