It remains unclear if the effort to enlist companies like General Motors, Apple and Hanes constitutes an effective strategy. WASHINGTON — President Trump’s refusal to invoke the Defense Production Act to commandeer resources for the federal government is based on a bet that he can cajole the nation’s biggest manufacturers and tech firms to come together in a market-driven, if chaotic, consortium that will deliver critical equipment — from masks to ventilators — in time to abate a national crisis. Over the past five days, after weeks of minimizing the virus and dismissing calls to organize a national response, administration officials have been pulling executives into the White House Situation Room, and connecting them by phone, in a desperate effort to unlock existing supplies and ramp up new production. Rear Adm. John Polowczyk has been plucked from the staff of the Joint Chiefs, where he is a senior officer for military logistics, to run the effort to build a supply chain. And Peter Navarro, the White House trade adviser, is also playing a leading role. The government has essentially thrown out its existing playbook for dealing with pandemics, seizing the issue from the Depart...