“Hunter, you know nothing about energy, you know nothing about China, you know nothing about anything, frankly,” Trump said to a near-capacity crowd. “Hunter, you’re a loser.”

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Mocking Hunter Biden’s lack of public appearances, Trump bellowed: “Whatever happened to Hunter? Where the hell is he? . . . I have an idea for a new T-shirt . . . Where’s Hunter?”

Trump attacked the press for fact checking the allegations he has leveled against the Bidens noting they are often described as unsubstantiated. “It’s not unsubstantiated, you crooked son of a guns,” he said after repeating his exaggerated and misleading claims about the former vice president and his family.

Trump, who has fixated on the former vice president as a potential 2020 foe since Biden entered the race in April, is embroiled in an escalating battle with House Democrats as they pursue an impeachment inquiry over Trump pressuring the leader of Ukraine to investigate Biden and his son Hunter over what Trump claims were the younger Biden’s corrupt business dealings in the country.

Hunter Biden served for nearly five years on the board of Burisma, Ukraine’s largest private gas company, whose owner came under scrutiny by Ukrainian prosecutors for possible abuse of power and unlawful enrichment. Hunter Biden was not accused of any wrongdoing in the investigation. As vice president, Joe Biden pressured Ukraine to fire the top prosecutor, Viktor Shokin, who Biden and other Western officials said was not sufficiently pursuing corruption cases. At the time, the investigation into Burisma was dormant, according to former Ukrainian and U.S. officials.

During the raucous rally — interrupted frequently by pro-Trump chants, cheers and boos as protesters were hauled out of the arena — the president ramped up his attacks on Biden and paid scant attention to other potential 2020 Democratic challengers, even as the former vice president has faltered lately in polling.

Biden “was never considered smart,” Trump said. “He was never considered a good senator. He was only a good vice president because he figured out how to kiss Barack Obama’s ass.”

Trump’s own vice president, Mike Pence, has been criticized for being too obsequious to the president.

“I’d love to run against him, to be honest,” Trump said of Biden.

Biden responded late Thursday after a town hall meeting in Los Angeles, writing in a Twitter post addressed to Trump: “I spent my night at the HRC [Human Rights Campaign] forum talking about the fundamental respect every human being deserves. You spent yours showing how little respect for anyone else you have. America is so much stronger than your weakness.”

Trump also fixated on the Democrats’ impeachment inquiry, attacking House Speaker Nancy Pelosi (D-Calif.) and House Intelligence Committee Chairman Adam B. Schiff (D-Calif.) and predicting that the Democrats’ “brazen attempt to overthrow our government will produce a backlash at the ballot box, the likes of which they have never, ever seen before in the history of our country.”

That claim comes even though recent polling has indicated that public opinion is turning against Trump. A Fox News poll released Thursday showed that 51 percent of voters want to see Trump impeached and removed from office.

At the rally, Trump insisted: “Polls are no different than crooked writers.”

Trump’s fire in Minnesota was expected to be trained on Rep. Ilhan Omar (D-Minn.), who represents the Minneapolis district where the rally was held. But he also elicited boos after mentioning Somali refugees more broadly.

“Leaders in Washington brought large numbers of refugees to your state from Somalia,” Trump said, at which point a sizable portion of the crowd booed, “without considering the impact on schools and communities and taxpayers.”

Minnesota is home to the largest concentration of Somali immigrants of any state — accounting for about 1 percent of the state’s population.

Trump also mocked Omar, the first Somali American in Congress. “How the hell did that ever happen?” he said of her election, adding: “Congresswoman Omar is an America-hating socialist.”

While Trump talked about Omar, images of her in a headscarf flashed on the arena’s screens.

Trump has attacked Omar many times before, including a racist taunt earlier this year that she and three other minority Democratic congresswoman should “go back and help fix the totally broken and crime infested places from which they came.” At a July rally, a crowd in North Carolina responded to his attacks by chanting, “Send her back!”