President Donald Trump continues to press foreign leaders to investigate one of his top political rivals, Joe Biden, suggesting Thursday that both the Ukrainian and Chinese governments look into the former vice president and his son.

“I would say President [Volodymyr] Zelenskiy, if it was me, I would start an investigation into the Bidens,” Trump told reporters as he departed the White House for a health policy event in Florida. “It’s a very simple answer.”

But the day before, during a joint news conference with his Finnish counterpart, Trump refused to answer a wire reporter’s repeated questions about just what he wanted Zelenskiy to do vis a vis the Biden father and son. House Democrats and a list of legal experts say his ask on a call with Zelenskiy to probe the Bidens amounted to a request for a personal political gain — to them, likely a violation of federal law.

The president again went hard after Biden, whom multiple public opinion polls show leading Trump in a hypothetical head-to-head general election race.

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In true defiant Trump fashion, he ignored criticism about asking Zelenskiy on a July 25 call that prompted House Democrats’ impeachment inquiry to “do us a favor” by investigating Biden after the Ukrainian leader had mentioned a desire to buy more U.S.-made anti-tank missile systems.

Instead, the president pressed a second foreign government to look into the 2020 Democratic frontrunner who tells voters almost daily he is the lone candidate who can prevent a second Trump term. And a Communist one at that, notably.

“China should start an investigation into the Bidens,” Trump said, bringing up Hunter Biden’s business dealings there unprompted by reporters. “I’m sure that President Xi doesn’t like being under that kind of scrutiny … where billions of dollars went out of his country … to a guy who just got kicked out the Navy,” Trump said, referring to reports that Hunter Biden was discharged from the service for failed drug tests.

“You know what they call that?” Trump asked rhetorically. “They call that a payoff.” He was not specific, however, about just who or what company in China alleged paid off the former vice president’s son nor why they would have done so.

His implication is someone in China offered Hunter Biden a big payment, possibly to influence his father and U.S. policy toward its top economic rival and lender.

Kate Bedingfield, the Biden campaign’s communication director, slammed Trump’s Thursday comments in a statement.

“Donald Trump is flailing and melting down on national television, desperately clutching for conspiracy theories that have been debunked and dismissed by independent, credible news organizations,” she said, referring to the Ukraine corruption charges. “It could not be more transparent: Donald Trump is terrified that Joe Biden will beat him like a drum.”

The former vice president himself fired back at Trump on Wednesday.

“Let me make something clear to Trump and his hatchet men and the special interests funding his attacks against me: I’m not going anywhere,” Biden said during a campaign event Wednesday in Nevada.

“You’re not going to destroy me,” he added, speaking directly to the man whose job he wants. “And you’re not going to destroy my family. I don’t care how much money you spend or how dirty the attacks get.”

A day later, their war of words continued.

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“I think Biden is going down,” Trump said over the loud hum of Marine One’s engines on the White House’s South Lawn. “You might find out there are other countries they scammed. … They really scammed the USA, and that’s not good.”

The president pinned China’s trade practices toward Washington — which he long has called “unfair” — likely were shaped by former officials like Biden, whom he contends Beijing calculated they could bribe and push around.

RealClearPolitics’ average of a handful of polls gives Biden a 7.7-percentage point lead over Trump, and the president on Wednesday said he would prefer to run against Biden over the other top Democratic 2020 candidates.

“I’d rather run against Biden than almost any of those candidates,” Trump said Wednesday. “And I think they’re all weak. But I think Biden has never been a smart guy and he’s less smart now than he ever was.”

His rolling, seemingly-never-ending battles with House Democrats and Biden overshadowed the visit of Finnish President Sauli Niinisto on Wednesday. During a joint press conference, even Finnish reporters joined their U.S. counterparts in peppering Trump with questions about the impeachment inquiry.

The American president appeared agitated, even sometimes flustered and angry. The spectacle unfolding before Niinisto prompted him to offer the embattled American president some advice during his opening remarks.

“Mr. President, you have here a great democracy,” Niinisto said. “Keep it going on.”