Just before President Joe Biden took office, he asked Americans to "mask up" for 100 days.

Biden said he would work with mayors and governors in red and blue states to ask them to require masks.

"This is not a political issue," Biden said, days before he was inaugurated.

But masks became a political issue in 2020 early in the pandemic when President Donald Trump spread falsehoods about masks and mocked mask wearing. Mask resistance by some members of the public and politicians have continued this year, posing an obstacle to Biden's campaign promise to implement mask mandates nationwide by working with governors and mayors.

After Biden took office in January, he issued orders requiring masks in federal buildings and on airplanes and trains. In February, Biden announced his administration would deliver 25 million masks to community health centers, food pantries and soup kitchens nationwide. 

But Biden doesn't have the authority to issue mask mandates for cities and states, and during his first 100 days, we saw many states back away from mask mandates.

Adriane Casalotti, a spokesperson for the National Association of County and City Health Officials, said the reduction of cases, the vaccine roll out and pandemic fatigue all contributed to decisions about mask rules. 

"I'd note that from a public health perspective, we are not out of the woods in any measure to make these changes yet based on those factors," Casalotti said. "The mandates on transportation are very meaningful, however, and help prevent spread there while also signaling that these efforts are still necessary."

About half of the states have mandatory mask restrictions as of mid-April, according to state trackers by the New York Times and AARP. Some states that dropped the mandate replaced it with language encouraging, but not requiring, use of masks.

Texas Gov. Greg Abbott, a Republican, was among the governors to lift the state's mask mandate this spring, although his order "strongly encouraged" people to wear masks.

"I just announced Texas is OPEN 100%. EVERYTHING," Abbott tweeted March 2.

Alabama Gov. Kay Ivey said she would personally continue to wear a mask when she lifted the statewide order as of April.

"There is no question wearing masks has been one of our safest tools in preventing the spread of the virus," said Ivey, a Republican. "When we lift the mask order, I will continue to wear my mask while around others and will strongly urge my fellow citizens to use common sense and do the same thing, but at that time, it will become a matter of personal responsibility and not a government mandate."

The end of statewide mask mandates in some states does not mean that there are no mask rules anywhere, although compliance with mask wearing varies. Some businesses have continued to require masks, and some city or county officials continue to mandate mask use, for example in the city of Austin, Texas. The White House pointed to a New York Times article in March that showed some officials continued to encourage mask use, including the Republican mayor of Arlington, Texas. 

One more point about Biden's promise: We wondered about the outcome of the Transportation Security Administration's announcement that individuals who violated mask rules on commercial and public transportation. TSA said it would fine violators starting at $250 for the first offense up to $1,500 for repeat offenders. We asked a TSA spokesperson how many people had been fined, and the spokesperson told us that data isn't available until legal proceedings are completed. However, the spokesperson told us that since Feb. 2, transportation system operators have reported about 1,000 passengers for refusing to wear a face mask among millions of passengers.

Back to Biden's promise: Biden has taken the steps available to him to require masks on federal property and airplanes and to send masks to vulnerable populations. But during Biden's first 100 days, we saw some states move in the opposite direction and drop mandates, although in some instances officials continued to encourage mask use, or require them on a local level.

We rate this promise Compromise. 

RELATED: Mask skeptics ask questions. PolitiFact answers

President Joe Biden, on his first days in office, issued orders requiring masks in federal buildings and on airplanes.

Biden's Jan. 21 order to protect travelers requires people to wear masks in airports, commercial aircraft, trains and public maritime vessels and intercity buses. It also requires travelers seeking to enter the United States from a foreign country to test negative for COVID-19 before entry, although the U.S. Centers for Disease Control and Prevention announced a similar requirement  before Biden took office.

Airlines have been requiring passengers to wear masks on board and had the option to ban from flights any who refuse, but the latest federal order gives them an extra tool.

A day earlier, Biden ordered that all individuals "in federal buildings and on federal lands should all wear masks, maintain physical distance, and adhere to other public health measures" as provided in CDC guidelines.

The part of Biden's order that could prove the most challenging, however, is his directive to federal officials to engage with state and local officials to maximize mask wearing and other public health practices. That's because boosting support for wearing masks is largely dependent on state and local leaders.

Lawrence Gostin, a health law professor at Georgetown University, said that while the president can require the wearing of masks on federal buildings and during interstate travel, he does not have authority to issue a national mask mandate.

That power is left to state officials, which is why the Biden administration is reaching out to governors.

During the Democratic National Convention in August, Biden said, "We'll have a national mandate to wear a mask, not as a burden, but to protect each other."

The Congressional Research Service in August issued a report cautioning that enforcement of a nationwide mandate could be restricted by the Constitution and other laws, including the Religious Freedom Restoration Act of 1993, which requires courts to grant certain religious exemptions.

Most states have mask mandates, according to a New York Times analysis. In the other states, some cities or counties have set their own rules. Biden may struggle to sway some states to issue statewide mask mandates. 

"I'm opposed to mandates, period," Florida Gov. Ron DeSantis, a Republican, told reporters Nov. 30. "I don't think they work. People in Florida wear them when you go out. I mean, they don't have to be strung up by a bayonet to do it. Fining people is, I think, totally overboard."

Some governors have said mask wearing should be a personal choice, including South Dakota's Republican Gov. Kristi Noem.

"Gov. Noem has been very clear on this subject: She does not support mask mandates," spokesman Ian Fury told PolitiFact.

 Masks became a partisan issue in 2020 as President Donald Trump spread falsehoods about masks and mocked mask wearing. Public health experts said Biden's mask order is a welcome step, but whether it will lead to more mask orders in states or cities remains to be seen.

"I am not sure that we will see more state or local mask mandates as a result, but certainly having a president that supports science-based COVID prevention strategies such as mask wearing helps stress the importance of face coverings as a common sense strategy to help stop the spread of COVID," said Michael R. Fraser, CEO of the Association of State and Territorial Health Officials.

A new, more transmittable variant of the coronavirus and the surge in cases could inspire more mask mandates, said Adriane Casalotti, a spokesperson for the National Association of County and City Health Officials. 

"We are still a very divided country and so there may be some ability to move individual areas, but the politics on the ground will still play a role," Casalotti said. 

Health officials largely agree that wearing a face mask, coupled with social distancing and frequent hand-washing, is more protective than going unmasked. The CDC recommends that people wear masks in public settings, including on public transportation, at events and gatherings, and anywhere they will be around other people. 

We will watch efforts by Biden to expand mask use nationwide, but his orders are a first step. We rate this promise In the Works.