For months, Gov. Kim Reynolds of Iowa saw little need to intervene in the choices of Iowans, who she insisted could make their own decisions about whether to wear a mask to protect against a dangerous pandemic.

“No, I’m not going to mandate masks,” she said this summer, dismissing the order as an unenforceable “feel-good” measure. “I believe in Iowans,” she said again in September.

Weeks later, as coronavirus cases climbed precipitously, she stood barefaced onstage at a rally for President Donald Trump and threw “Make America Great Again” hats into a crowd.

But as the virus ravaged her state and hospitals filled to the brink, Reynolds abruptly reversed herself this week and began requiring masks indoors. She joined a wave of Republican governors who are newly and at times reluctantly wielding the power of their offices as the coronavirus erupts to crisis levels across the United States. On Wednesday, the country passed 250,000 virus-related deaths, with no end in sight.

“No one wants to do this,” Reynolds said in a live address to Iowa, which has the third-highest rate of new cases in the nation. “I don’t want to do this.”

Reynolds has offered little insight into her reversal, but interviews with more than a dozen political, health and business leaders in Iowa — some of whom the governor consulted before issuing the order — show that her hand was forced by a spiraling hospital crisis. As pressure built from doctors, mayors and even people serving in her own administration, the message was clear: If she did not act, Iowa’s hospitals could soon be overflowing with coronavirus patients, leaving few ambulances, beds or doctors left to care for anyone else.

“It says that it’s serious,” said A.J. Spiker, a former chairman of the Iowa Republican Party who worked alongside Reynolds when she was the lieutenant governor, describing a particularly emotional and urgent tone in her announcement. “Just the way she said things as she spoke, I know her well enough to know that she’s concerned.”

Reynolds’ reversal comes as other Republican governors are moving to embrace directives they once eschewed. The governors of North Dakota and Utah have also issued mask mandates in recent days, while still resisting the more aggressive approach taken by Democrats who are again shutting down indoor dining at restaurants and closing other businesses where the virus is known to spread.

The changes reflect both the increasing threat the coronavirus poses in the United States, as well as the shifting political landscape.

The country is recording more than 158,000 new cases per day on average, the highest so far of the pandemic; more than 76,000 people are hospitalized with the virus nationwide, far higher than earlier peaks; and deaths are again on the rise. Trump has largely ceded the pandemic response to governors, and the states where the virus is emerging at the highest rates — North Dakota, South Dakota and Iowa — are all Republican-led.

In Iowa, Reynolds had been facing pressure for months — from mayors, doctors, nurses and farmers, who feared that rising cases could lead to interruptions to the food supply chain in a state where agriculture and meat processing are major industries.

Like most other governors, Reynolds closed down businesses in the spring, but she resisted issuing a stay-at-home order and did not require masks as communities reopened.

Now, as the virus surges across the Midwest, more than 4,100 people are testing positive for the virus in Iowa every day on average, an 86% increase over the past two weeks. Hospitalizations have doubled in the same period, and coronavirus patients now make up one out of every four hospitalizations in the state.

The crisis led to a significant move last week, when the Iowa State Board of Health, whose members Reynolds appointed, urged her to issue a mask mandate. The board’s vote was itself a sign of how the virus’ worsening toll has forced people to change their thinking. Board members, most of whom are Republicans and work in health care, had discussed face coverings at previous meetings but did not come out in favor of a mandate.

At the most recent meeting, however, they voted 7-2 to encourage the governor to issue the order.

The governor began moving to tighten restrictions last week, requiring masks in some circumstances and tightening the rules on attendees at youth sports games and other events.

She implemented a full mask order this week, citing rising hospitalizations.

“If Iowans don’t buy into this, we lose,” Reynolds said, warning that the hospital system could collapse. “The cost in human life will be high.”

Still, her order contains a number of exceptions. People must wear a mask in indoor public places, but only if they will be within 6 feet of another person for at least 15 minutes. Indoor dining is still permitted. School districts are allowed to decide for themselves whether or not to require masks; about one third of Iowa’s school districts currently do not require them.

Health experts say masks are crucial to stopping airborne virus particles from spreading, and protect both the wearer and others.

At a news conference Tuesday, Reynolds at one point seemed to equivocate on the effectiveness of masks, saying “there’s science on both sides” and “if you look, you can find whatever you want to support wherever you’re at.” But when asked how Iowans should sort through the range of exceptions, she was straightforward.

“If they’re confused,” she said, “I’d say just put the mask on.”

Scoffing at the mixed messaging, Democrats in Iowa criticized the order as a half-measure that would do little to quell a growing crisis.

“This would have been a good thing to do in early October,” said Rob Hogg, a Democratic state senator in Iowa who was among those who wondered whether Reynolds, an ally of Trump, may have been reluctant to take action earlier and risk angering conservatives or the president in the weeks before the election.

A spokesman for Reynolds said that the election was not a factor in her decision. He declined to elaborate on the shift in her thinking and said she was not available for an interview.

But as the situation deteriorated in Iowa and across the country, her perspective seemed to change.

Mayor Mike Matson of Davenport, Iowa’s third-largest city with a population of about 101,500, said he had been in touch with the governor in recent weeks and had relayed the concerns of hospital administrators and health officials who were growing increasingly panicked about rising hospitalizations, ICU space and the pressures on hospital staff.

“She has been very gracious to listen to me,” said Matson, a Democrat, who said he had spoken with the governor by phone and via text message. “I just wanted her from my perspective to know how serious it is.”

“I was glad she did it,” he said, but he added: “We waited a little long.”

Mayor Bob Scott of Sioux City, whose position is nonpartisan, said he similarly wished that Reynolds had issued the order sooner and worried that the crisis was already spinning out of control.

“This should have happened three weeks ago,” he said, pointing to the dwindling room at hospitals. “We don’t have that many beds left.”