WASHINGTON (AP) — President Donald Trump and challenger Joe Biden will compete for TV audiences in dueling town halls on Thursday night instead of meeting face-to-face for their second debate as originally planned.

The two will take questions in different cities on different networks: Trump on NBC from Miami, Biden on ABC from Philadelphia. Trump backed out of plans for the presidential faceoff originally scheduled for the evening after debate organizers said it would be held virtually following Trump's coronavirus diagnosis.

The town halls offer a different format for the two candidates to present themselves to voters, after they held a chaotic and combative first debate late last month. But Trump, speaking on Fox Business on Thursday morning, kept up his same tone, calling Biden "mentally shot," a "liar" and a "corrupt politician."

He said that "some people said I was rude" in the first debate, "but you have to be rude. The guy's a liar."

He said NBC asked him to do the town hall.

"It's a different audience and it's good for me to have a different audience," he said.

As the pace of the campaign speeds up in its final weeks, the two candidates first are taking care of other electoral necessities Thursday: Trump had a midday rally in battleground North Carolina, and Biden was raising campaign cash at a virtual event.

During his fundraiser, Biden warned supporters that Trump is "going to throw everything but the kitchen sink at me" and will deliver "an overwhelming torrent of lies."

Biden's son, Hunter Biden, came under scrutiny this week following a New York Post report outlining an email Hunter allegedly received from a Ukrainian businessman discussing a meeting with the elder Biden. Biden's campaign has said the meeting never happened, and experts have raised questions about the veracity of the emails.

Indeed, with just 19 days until Election Day, there remains ample time for unexpected developments to throw off the candidates' plans — like they did Thursday, when Biden campaign manager Jen O'Malley Dillon announced the campaign was canceling running mate Sen. Kamala Harris' in-person campaign events through Sunday "out of an abundance of caution" after two staffers tied to the campaign tested positive for the coronavirus.

The campaign told reporters Thursday morning that Harris' communications director and a flight crew member tested positive after a campaign trip to Arizona last week, during which Harris and Biden campaigned together throughout the state.

Biden and Harris both have tested negative multiple times since then. The campaign said Thursday morning that Biden had again tested negative for the virus and that Harris was never in close contact with the staffers. But in an effort to draw a contrast with Trump, the campaign has emphasized its strict protocols in dealing with the virus and said it'd be moving Harris' campaign events online whenever possible in the next few days.

Meanwhile Trump, after recovering from his own bout with the coronavirus, has been trying to shore up support from constituencies that not so long ago he thought he had in the bag: big business and voters in the red state of Iowa.

In a Wednesday morning address to business leaders, he expressed puzzlement that they would even consider supporting Biden, arguing that his own leadership was a better bet for a strong economy. Later, the president held his third campaign rally in three nights, this time in Iowa, a state he won handily in 2016 but where Biden is making a late push.

"I know I'm speaking to some Democrats, and some of you are friends of mine," Trump said in a virtual address to the Economic Clubs of New York, Florida, Washington, D.C., Chicago, Pittsburgh and Sheboygan, Wisconsin. Should Biden be elected, he continued, "you will see things happen that will not make you happy. I don't understand your thinking."

During his decades in the Senate representing Delaware, a center for the credit card and banking industries, Biden built relationships and a voting record in the business sector that has raised suspicion on the left but provides Wall Street with a measure of ease at the prospect of a Biden administration.

After being sidelined by the coronavirus, Trump resumed a breakneck schedule this week, with aides saying he is expected to travel and host campaign rallies every day through Nov. 3. Trump has appeared hale in his public appearances since reemerging from quarantine, though at moments during his economic address on Wednesday his voice was raspy.

In Iowa, Trump tossed away his tie and donned a red hat to fight off the stiff breeze on the airport tarmac. He made a direct appeal to the state's farmers, saying that he was responsible for $28 billion in aid designed to help offset damage stemming from his trade war with China. "I hope you remember that on Nov. 3," Trump said.

But after years of farmers supporting him despite the trade war, some Republicans say Trump's renewable fuel policy has sown some doubt.

Trump's Environmental Protection Agency granted dozens of waivers to petroleum companies seeking to bypass congressional rules requiring the level of the corn-based fuel additive ethanol that gasoline must contain. He has recently denied more waiver requests, but the EPA's previous action removed about 4 billion gallons of ethanol demand, resulting in the closure — at least temporarily — of more than a dozen ethanol plants in Iowa.

Biden has stepped up campaign travel in the past week, with visits to Arizona, Nevada, Florida and Pennsylvania, where he drove his consistent campaign message that Trump has mishandled the coronavirus pandemic.

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Barrow reported from Wilmington, Del., and Madhani from Chicago.