"Nobody has been tougher on China than me," President Trump proclaimed at Tuesday's coronavirus briefing.

When the Trump administration has been criticized for how it has handled the coronavirus outbreak, the president has been inclined at times to blame the Chinese and then accuse his Democratic opponent Joe Biden of being "weak on China."

Biden's campaign has been trying to turn that argument back on Trump, seeing lots of material to work with as the president has touted an improved trading relationship with China.

A side effect of the coronavirus outbreak is that China has become a powerful election year issue. Who's "tough on China" has taken on a broader political meaning, with a fight not just about longstanding trade and labor concerns, but also a global health pandemic originating in that country and whether the U.S. response was adequate.

A recent ad from a super PAC supporting Trump plays menacing music as a narrator warns the audience that "for 40 years Joe Biden has been wrong about China."

An image of Biden with his son Hunter flashes across the screen, and the ad ends with an image of the Chinese flag billowing over Biden's face. The Trump campaign has often pointed to Hunter Biden's past business dealings in China as evidence of corruption, and the focus on China allows it to dive back into broader criticism of the younger Biden's foreign business dealings.

After that ad aired, the Biden campaign responded with one of its own, saying: "Trump rolled over for the Chinese."

"Trump praised the Chinese 15 times in January and February as the coronavirus spread across the world," the narrator says as images of Trump flash across the screen.

That followed an ad from the Democratic super PAC American Bridge criticizing Trump for "giving China his trust."

But this "who's tougher on China" ad war began in earnest with an inflammatory video the Trump campaign released in early April that implied that Gary Locke, the former governor of Washington and U.S. ambassador to Beijing, was Chinese, even though he was born in Seattle.

That ad showed an image of Biden clinking wine glasses with China's leader Xi Jinping as it warned viewers that "Biden protected China's feelings."

The tit for tat is indicative of how China has become a central campaign issue. But perhaps more importantly, it shows how there seems to be bipartisan agreement that projecting a strongman image against China has political benefit.

A recent report from the Pew Research Center finds that more Americans have a negative attitude toward China now than at any other point since they began tracking this question in 2006. The polling shows that two-thirds of Americans now have a negative view of China; that compares to just 47% in 2017.

"The future is going to involve a lot of second-guessing about the relationship between the U.S. and China. That's clear," said GOP pollster Frank Luntz. "Who people finally decide they trust more, I think that's up for grabs."

He predicts that China will be the second-most important issue in the presidential campaign, behind only the handling of COVID-19.

And both campaigns, Luntz says, understand that political uncertainty.

"Both of them are going for the jugular," he added. "Both of them are trying to show that the other side is weak on China or misinterprets the intentions of China or would handle China badly in the future."

Some Trump supporters have begun calling the presumptive Democratic nominee "Beijing Biden."

Many Democrats have praised Biden's most recent ad as a brilliant show of force that rips apart the president's attempt to prove that he held China accountable for the virus.

"I am delighted he pushed back," said Democratic pollster Stan Greenberg. "I think it's right to define the issue and say we're not going to take punches on this question."

Greenberg said Biden needed to respond to Trump's attempt to "rewrite history" on China, specifically at the outset of the pandemic.

"It's going to make it difficult for [Trump] to keep engaging this issue when he's not been very transparent, and been so weak in dealing with China," he added. "So I think that was an important battle to win early."

But he doesn't believe that who's tougher on China is actually the framework in which the general election will be waged.

The escalation of these ads worries Christine Chen, executive director of APIAVote, a political engagement group focused on Asian and Pacific Islander Americans.

"The last six weeks we've seen an increase of hate crimes, hate incidences, blaming of anyone that looks of Asian or Chinese," she said. Chen is concerned that both Biden and Trump's ads have exacerbated the environment.

"I understand the natural instinct is for a campaign to respond to another campaign or another ad," she said, referring to Biden's recent China ad.

But Chen thinks the tone was a mistake. "I don't think Biden was intending to be xenophobic," she added. "But at the same time, I think it was a misstep."

A couple of other Democratic activists NPR spoke with were far more critical, wondering why Biden, they say, had stooped to Trump's level. They felt that Trump consistently used xenophobic language, but Biden's ad troubled them because, intentional or not, it seemed to engage in similar language.

They pointed to a specific line in the ad about Trump's travel ban where the narrator says: "Trump let in 40,000 travelers from China into America after he signed it. Not exactly airtight."

"It's not a race to see who can be more tough on China or the Chinese people," said Alton Wang, a Los Angeles-based community activist. "I think it's a race to see who could be a more competent president."

In a statement, the Biden campaign pointed out that it has "held Donald Trump's feet to the fire over his use of xenophobic labels."

The statement also said, in part, "Our ad levels substantive and deserved criticisms at Donald Trump for believing discredited Chinese government propaganda about containment of the virus, something Joe Biden publicly warned him not to fall for."

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