Insurers, which had been arguing in favor of the enrollment period, had been hopeful just a few days ago that the White House might announce such a step. But the situation suddenly became “fluid,” in the description of one executive. Another described the administration as divided about whether to proceed, especially given the president’s support for the lawsuit that would overturn the law.

Numerous other health care provider and consumer groups, including the American Diabetes Association, Families USA and the New Hampshire Nurses Association, wrote a joint letter to the administration last month asking it to establish a special enrollment period. The groups argued that forcing people to verify eligibility “would not only delay care receipt, it would deter enrollment by healthy customers, endangering the individual-market risk pool,” the grouping of customers that determines what the insurers charge for a policy.

Governors of several states also asked the administration to grant a special enrollment period, including Republican governors in Arizona and New Hampshire, and Democratic ones in Oregon, Michigan and New Jersey.

Many Democratic politicians criticized the decision Wednesday as insensitive to the needs of the public in a crisis, including Joe Biden, who leads the race for the Democratic presidential nomination. The Democratic Congressional Campaign Committee also released a statement, suggesting it may become a campaign issue. Democrats made health care a centerpiece of many House races in the 2018 midterm elections.

“In the midst of a global pandemic, Washington Republicans continue their crusade against the health and safety of the American public,” said Fabiola Rodriguez, a spokeswoman for the group, in the statement. “By blocking uninsured Covid-19 patients from getting health care, Trump and his allies have decided to bankrupt American families. The American people deserve to know if House Republicans will stand up for the millions of Americans who face the challenge of being jobless and uninsured during the Covid-19 pandemic.”

Both Democratic and Republican members of Congress had also urged the administration to consider a special enrollment period. But Congress declined to require such an enrollment period in its last round of coronavirus legislation, instead leaving the decision to federal officials.

In a statement Wednesday, Senator Cory Booker of New Jersey recommended that Congress include a special enrollment provision in its next round of coronavirus legislation. He had also proposed such language be included in the last bill. “At a time when our health care system is already under enormous strain, it makes no sense to willingly allow even more individuals to go without coverage,” he said.