WASHINGTON — The White House and lawmakers scrambled on Thursday to flesh out details of a $1 trillion economic stabilization plan to help workers and businesses weather a potentially deep recession, negotiating over the size and scope of direct payments to millions of people and aid for companies facing devastation in the coronavirus pandemic.

Senate Republicans, racing to put their imprint on the crisis response, unveiled a package that would provide hundreds of billions of dollars in loans to big corporations and small businesses, large corporate tax cuts and checks of up to $1,200 for taxpayers. The plan would also place limits on a paid-leave program enacted this week to respond to the crisis.

But the 247-page measure, the product of a feverish round of negotiations among Republicans, was all but certain to face opposition from Democrats who have pressed for more generous paid-leave benefits and targeting help to workers and families rather than large corporations.

The details emerged as Washington grappled with the dimensions of an extraordinary government rescue effort that is likely to last for many months. At the White House, President Trump said he would be open to having the government take equity stakes in companies that require federal help, a move that would be unpopular with shareholders and would give the government more oversight over businesses.