Coronavirus government response updates: Trump claims to have worn mask, but only off camera

President Donald Trump traveled to the election battleground state of Michigan to visit a Ford plant converted to make ventilators -- and as he did -- it was an open question whether he would wear a mask as everyone else who works or visits there is required to do by law.

"Well, I don't know, we’re gonna look at it," Trump said when asked as he left the White House.

When he eventually toured the plant, he wasn't wearing a mask when speaking with Ford officials -- at a distance -- but then told reporters he had worn one earlier, out of their sight and camera-range.

"I didn't want to give the press the pleasure of seeing it," he said.

"I was given a choice" about whether to wear one, Trump said, and when asked about what message he was sending, he responded, "I think it sets an example both ways."

The White House is playing down new findings from Columbia University researchers that 36,000 lives would have been saved had Trump and governors acted a week earlier in March to impose social distancing and other restrictions -- and that a vast majority of the nation's deaths -- some 83 percent -- would have been avoided if stay-at-home limits had been put in place two weeks earlier.

Trump dismissed it as "a political hit job."

The findings were reported in The New York Times.

And as the U.S. death toll approaches 100,000 as the nation heads into Memorial Day weekend, House Speaker Nancy Pelosi and Senate Majority Leader Chuck Schumer have sent a letter to President Trump calling on him to order all U.S. flags on government buildings lowered to half-staff on that "sad day of reckoning."

Here are Thursday's most significant developments in Washington so far:

• President Trump visited a Ford plant in Michigan, his third recent trip to an election battleground state
• Trump wasn't seen wearing a mask as the company rules and Michigan law require
• The president has backed down from threat to cut aid to Michigan over mail-in voting
• Trump calls new Columbia University study that finds imposing restrictions a week earlier would have saved 36K lives a 'political hit job'
• House Speaker Pelosi, Senate Minority Leader Schumer call on Trump to order flags lowered when death toll hits 100K

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From earlier today:

Trump heads to Michigan ventilator facility, unclear whether he'll wear mask

President Trump leaves the White House again -- this time to tour a Ford plant, converted to making ventilators, in Ypsilanti, Michigan -- his third visit to a 2020 election battleground state in the past couple of weeks following trips to Pennsylvania and Arizona.

It's unclear whether he'll wear a mask as company rules and Michigan law require him to do.

The state's Democratic attorney general said she won't try to block Trump if he doesn't, but said she might take action against companies and other organizations that allow him to go without a mask and might try to stop future visits.

When asked on Tuesday about whether he would wear a mask, Trump said it depends on how close he comes to other people.

"Well, I don't know, we’re gonna look at it," Trump said when asked as he left the White House Thursday. "A lot of people have asked me that question. I want to get our country back to normal. I want to normalize."

Ford officials have indicated they will let hm bend the rules and go without a mask if he chooses.

Vice President Mike Pence, who wore a mask in similar setting after being criticized for not doing so, did not wear a mask at a Florida burger joint Wednesday during a photo op to highlight restaurants starting to reopen in that state.

---ABC News' Ben Gittleson

Trump calls study findings earlier action would have saved 36K lives 'a political hit job'

President Trump has dismissed a new study estimating tens of thousands of lives would have been saved if he and governors had imposed restrictions a week or two earlier in March as "a political hit job."

The new findings from Columbia University researchers say that had the U.S. begun imposing restrictions one week earlier in March, 36,000 lives would have been saved and some 54,000 if they'd been imposed two weeks earlier.

"Columbia's an institution that's very liberal," Trump said as he left the White House. Without providing any evidence, he added, "I think it's just a political hit job."

Earlier Thursday, a White House spokesman pointed a finger at China.

“What would have saved lives is if China had been transparent and the World Health Organization had fulfilled its mission,” White House deputy press secretary Judd Deere said in a statement responding to a report in The New York Times.

“What did save American lives is the bold leadership of President Trump, including the early travel restrictions when we had no idea the true level of asymptotic spread and the greatest mobilization of the private sector since World War II to deliver critical supplies to states in need and ramp up testing across the country that has placed us on a responsible path to reopen our country,” he said.

Additionally, a White House official said the “success” of responding to COVID-19 “has been built on the federal-state partnership, not a federal government coming in and telling governors and mayors what decisions to make for their communities when a bureaucrat in Washington has [no] idea what is best for them.”

“We made the best decisions possible for the health and safety of the American people with the information we had at that time,” the official said. “We aren’t looking back. We are moving forward.”

---ABC News' Ben Gittleson

Pelosi, Schumer call on Trump to order flags lowered when US death toll reaches 100K

As Memorial Day nears, and with the U.S. death toll now over 93,000 and the Centers for Disease Control and Prevention estimating it will reach 100,000 by the end of the month, House Speaker Nancy Pelosi and Senate Minority Leader Chuck Schumer have sent a letter to President Trump requesting he order flags on all public buildings lowered "on the sad day of reckoning."

Here is the text of their letter:

Dear Mr. President:

This weekend, we will observe Memorial Day an occasion of great importance as we honor the men and women who were willing to make the ultimate sacrifice for our country. We will always carry their memory in our hearts. We reserve Monday to give special remembrance to them.

As we pay our respects to them, sadly, our country mourns the deaths of nearly 100,000 Americans from COVID-19. Our hearts are broken over this great loss and our prayers are with their families.

Respectful of them and the loss to our country, we are writing to request that you order flags to be flown at half staff on all public buildings in our country on the sad day of reckoning when we reach 100,000 deaths. It would serve as a national expression of grief so needed by everyone in our country.

Thank you for your consideration of this matter of grave concern.

The White House has not responded.

---ABC News' Mariam Khan

What to know about coronavirus:

• How it started and how to protect yourself: coronavirus explained
• What to do if you have symptoms: coronavirus symptoms
• Tracking the spread in the US and Worldwide: coronavirus map