If Donald Trump insists on calling himself a wartime president, Joe Biden said, “Well, start to act like one.”

This was the charge the former vice president leveled at Trump from self-isolation in Wilmington, Del., on Monday. He stood alone behind a podium, stared into the web camera in his hastily constructed home studio, and offered a bit of a history lesson.

“To paraphrase a frustrated President Lincoln writing to an inactive General McClellan during the Civil War,” Biden explained, “‘If you don't want to use the army, may I borrow it?’”

It was the first of his shadow briefings, an attempt to contrast how he would handle COVID-19 with how the White House currently combats that pandemic. But Trump won’t let Biden borrow anything. He will have to win it come November, and for now, the Democratic frontrunner has made the global health crisis the defining issue of his campaign.

Acting like a wartime president, Biden argued, means using wartime powers. Flex the muscles of the federal government, he suggested — use the Defense Production Act.

A provision of Cold War vintage, the act allows the president to order private industry to mobilize for public defense. Trump has signed it. Trump has not, however, used all the vast powers the law affords him to rush the manufacture of medical supplies. This, Biden insists, is a failure.

"The president must use the Defense Production Act to radically increase the supply of goods needed to treat patients," Biden added. Restock FDR’s old Arsenal of Democracy, he suggested, not to fight geopolitical opponents this time, but to defeat a pathogen. In short, use those presidential powers to direct industry to build masks and face shields, tests and ventilators. And hurry.

This kind of message suits Biden. He was the vice president, he likes to remind voters, and he has the executive experience to get things done. The pandemic that has shut down much of the country, sent the markets into a freefall, and infected no fewer  than 33,404 Americans sets the table for this kind of argument. But even in his own home, away from the distractions of any audience, Biden stumbled at times before starting to ad-lib.

“Look, here’s the deal,” he said, leaning on a familiar phrase before going characteristically off-script. “We have to do what we did in the ‘40s and the ‘20s in 2020. And we can do that; we need to build a medical arsenal.”

The administration doesn’t exactly disagree. The president just says that he is building the arsenal without commandeering industry. He called Peter Navarro, his trade policy adviser, to the podium in the White House briefing room on Sunday to explain why his approach was preferable. “When you have a strong leader,” he argued, “you can take a light hand initially.”

According to Navarro, the Defense Production Act means both mobilizing industry and allocating resources. The private sector has stepped up on its own to produce necessary medical supplies, he said, while the federal government has made certain that products find their way to where they are most needed. It is why Pernod Ricard can switch from distilling liquor to producing hand sanitizer and how Hanes can retrofit factories to manufacture cloth masks.

“We are seeing the greatest mobilization in the industrial base since World War II,” Navarro said after citing those two examples. More aggressive government action might come later. For now, he said, “We are getting what we need without putting the heavy hand of government down.”

For a president derided for allegedly harboring authoritarian aspirations, Trump has shown little appetite for his emergency power. But why? Why would he not invoke the Defense Production Act when nurses and doctors are warning about a critical shortage of medical supplies and equipment that in some cases they need to keep patients from suffocating? Because, Trump said when pushed by reporters, the market is already gearing up on its own to meet demand. And besides, “We’re a country not based on nationalizing our business. Call a person over in Venezuela, ask them how did nationalization of their businesses work out? Not too well.”

Several critics were quick to argue that the Defense Production Act does not nationalize industry. It only allows the government to make contracts with companies and compel industry to “require acceptance and performance of such contracts.”

Sens. Chris Murphy of Connecticut and Brian Schatz of Hawaii introduced legislation less than 24-hours later “requiring the federal government to take over the medical supply chain.” Their bill would require the White House to “identify private sector capacity to help nothing less than 500,000,000 N95 respirators; 200,000 medical ventilators; 20,000,000 face shields; 500,000,000 pairs of gloves; and 20,000,000 surgical gowns in addition to other medical equipment deemed necessary.”

How the two Democratic senators arrived at those numbers or whether they’re realistic is not clear. Neither returned RealClearPolitics’ requests for comment. Like many others in the Senate, both have shut their Capitol Hill offices to practice the social distancing to slow the spread of the virus. While Congress debates an emergency stimulus package, Biden remains about 100miles northeast of the Capitol,self-isolating like most of the rest of the country and contemplating a way to run for president now that the traditional campaign trail has been all but closed.

Rallies and townhalls are public health liabilities. Online addresses and social media blitzes are the best and likely the only safe ways to reach voters. And so, as cities lock down and more people stay home from work, Biden has a captive audience. More than 230,000 watched his shadow briefing on a Monday morning when most Americans would otherwise be at work. He streamlined his message for the occasion.

“My point is not simply that the president was wrong. My point is that the mindset that was slow to recognize the problem in the first place, to treat it with the seriousness it deserved, is still too much a part of how the president is addressing the problem,” Biden argued.

“Let me be clear. Donald Trump is not to blame for the coronavirus, but he does bear responsibility for our response,” he added. “I, along with every American, hope he steps up and starts to get this right.”

Biden, meanwhile, will be watching, and critiquing, all the way to November.