With more than 1 million Americans known to have coronavirus, and polling showing a negative shift in Americans' attitudes toward China, the presidential candidates have ramped up attacks on each others' records related to the global superpower.

For President Donald Trump, the focus on former Vice President Joe Biden's record on China comes as he fights off criticism of his administration's response to the coronavirus pandemic. He has also ramped up his criticism of China’s handling of the initial coronavirus outbreak.

On the other side, Biden is using Trump's previously complimentary remarks about China as part of the argument that he is better qualified to lead the country through the pandemic and the recovery.

By pinning blame for coronavirus on China, Trump is looking to find traction as public opinion of his handling of the crisis has dipped. Biden has sought to exploit those openings, while touting his own dealings with the nation as vice president. And as the rhetoric escalates, advocates are also urging caution about the focus on China, given a rise in reports of discrimination directed at Asian Americans.

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Experts said the response from Biden signals a willingness to take a page out of Trump's playbook to get in front of the president's attacks.

"When someone punches you, you punch them back harder – that's kind of 101 out of the Trump campaign from the primary and the general in 2016," said John Della Volpe, director of polling at Harvard University's Institute of Politics. "To me, that was an element of that strategy from Biden. But you also have the relevant information of record over the last 90 days."

And the presidential campaign isn't the only race being touched by the escalation in China-related rhetoric.

A 57-page strategy memo for Senate Republicans' campaign arm, first reported on by Politico, advised candidates when asked about Trump's handling of the coronavirus pandemic, “Don’t defend Trump, other than the China Travel Ban – attack China."

Dueling ads, campaign memos

The elevation of China as a campaign issue escalated over the month of April.

The Trump campaign took aim first, slamming in tweets and ads Biden's initial criticism of Trump's ban on travel from China. Trump allies have referred to the former vice president as "Beijing Biden" while the president has increasingly accused China of concealing the seriousness of the coronavirus pandemic before it spread globally.

"We are not happy with China," Trump said at a Monday coronavirus task force news conference, adding that his administration would be pursuing investigations into China's handling of the pandemic.

In turn, the Biden camp has attacked Trump's praise of China early in the coronavirus pandemic as Americans were beginning to getting sick.

"Trump praised the Chinese government instead of taking action to combat the coronavirus," read a Monday email from the Biden campaign that extensively quoted from a Politico article titled "15 times Trump praised China as coronavirus was spreading across the globe."

The Trump campaign's first volley launched this month: an online ad called "Biden stands up for China."

It highlights Biden saying, "This is no time for Donald Trump's record of hysterical xenophobia" after Trump limited air travel from China in January, though Biden later clarified his position in support of the travel restrictions. The ad then pivots to the business dealings of Joe Biden's son, Hunter, in China.

"It is in our best self-interest for China to be able to prosper," the elder Biden is shown saying in a clip from a 2011 speech at Sichuan University in Chengdu, China, as ominous music plays. A caption then appears: "No. Just Biden's interest."

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But the Biden campaign quickly pushed back, using Trump's words, tweets and policy decisions to portray a president who had a blind eye to China. A little over a week later, the Biden campaign released its own ad and videos on social media to present its side of the story.

The Biden campaign accused Trump of trying to hide that he "failed to act," providing several rebuttals in its own ad released on April 18. It includes Biden's Jan. 27 op-ed in USA TODAY, before the outbreak spread in the U.S., where he wrote Trump's actions "left us unprepared" for a pandemic; remarks from a debate where Biden demanded American health authorities be allowed into China in a call for transparency; and reporting of 15 instances where Trump praised China, including a Jan. 24 tweet praising China's "efforts and transparency."

"Trump rolled over for the Chinese," a voice over in the the ad says.

"Look around," it continues later, noting the millions of people out of work and tens of thousands killed by COVID-19. "Donald Trump left this country unprepared and unprotected for the worst public health and economic crisis in our lifetime."

In a campaign memo distributed to Democratic officeholders earlier in April, Biden deputy campaign manager Kate Bedingfield unveiled four key talking points to frame Trump's response to the coronavirus. Atop the list: "The Chinese government."

"He praised its leader and did not fight anywhere near hard enough to get the facts," the memo reads.

In response, Trump campaign deputy press secretary Sarah Matthews said Trump has "always been resolute in taking early action," again pointing to Trump's travel restrictions on China.

"In contrast, before and during the coronavirus crisis, Joe Biden stood up for China, dismissed them as an economic threat, and initially opposed President Trump’s China travel restrictions," she said in a statement.

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Number of Americans who view China unfavorably grows

The focus on China, however, seems to have occurred simultaneously with a shift in public opinion on China and Chinese people.

A poll released last week by Pew Research Center showed about two-thirds of Americans have an "unfavorable" opinion of China, the highest ever proportion since Pew started asking the question in 2005. And a poll published Tuesday by the Center for Public Integrity and Ipsos showed about 3 in 10 Americans in the poll sample blaming China or Chinese people for the pandemic.

University of California, San Diego professor of political economy Victor Shih told USA TODAY the criticism of China follows a broader negative trend towards China in American politics.

"Things already were trending in a negative direction, even before the coronavirus," Shih said, noting the ongoing trade war between the United States and China, but the ongoing "China-bashing" was "doing real harm to the status of Asian Americans overall but especially Americans of Chinese descent."

Pew Research Associate Kat Devlin told USA TODAY it was "just within the last two years" that Pew had witnessed such a negative change in its data, lining up with the ratcheting up of rhetoric about the trade war between the two countries.

Devlin noted that a partisan shift had happened in their data, too.

In the past, Republicans had expressed more negative views of China, but "in the last two years we're now seeing majorities of Democrats and independents who lean Democratic also holding these unfavorable views."

Criticism over the ads on both sides

The attacks from both the Trump and Biden campaigns have not been without some criticism.

Trump's ad includes an image of former Washington Gov. Gary Locke, who is Chinese American, prompting criticism of the Trump campaign. Locke accused the Trump campaign of "fanning hatred," and the Biden campaign called for the ad to be taken down.

Biden's ad received positive reviews from some on the left, who praised Biden for punching back.

But others, particularly from the progressive left and some Asian American groups, disagreed with the Biden campaign's messaging and the focus on China from both campaigns.

ACLU lawyer Cecillia Wang responded to the Biden ad on Twitter, saying Biden was trying to "out-Trump Trump."

Christine Chen, executive director of Asian and Pacific Islander American Vote, called the Biden ad a "misstep" and the Trump ad "irresponsible" for including Locke.

"I understand the instinct for a campaign to respond directly to an opposing campaign's ad," Chen said, "and while I do not believe the Biden campaign meant to be xenophobic, the ad was still a misstep."

Rep. Judy Chu, D-Calif., the chair of the Congressional Asian Pacific American Caucus, told USA TODAY there was space for a conversation criticizing the Chinese Communist Party, but "making China as a whole a centerpiece of a political campaign, and doing so in a way that blames China for our problems, is only going to encourage more anger and xenophobia at a time when both are dangerously high."

"I encourage all parties to refrain from anti-China broadsides that put Asian Americans in harm’s way," she said.

Reach Joey Garrison (@joeygarrison) and Nicholas Wu (@nicholaswu12) on Twitter.