"I'm so glad that he obeyed the rules of the Walter Reed. You can't go see our veterans who are there without wearing a mask. Now, he's crossed a bridge," Pelosi told CNN's Dana Bash on "State of The Union." "That's an admission that if you're going to see our soldiers, you have to wear a mask. If you're going to be with our children, you have to wear a mask. If we want to stop the spread of the coronavirus, you have to wear a mask."
The California Democrat continued, "So hopefully by his example, he will change his attitude, which will be helpful in stopping the spread of the coronavirus."
The President's decision to wear a mask during his Saturday trip to the medical center comes after months of declining to publicly wear one -- against the recommendations of his own administration's public health experts.
Joe Biden campaign spokesman Andrew Bates responded to Trump's decision to wear a mask, saying the President "wasted" four months discouraging people from wearing masks while Biden "has led by example from the start."
"Donald Trump spent months ignoring the advice of medical experts and politicizing wearing a mask, one of the most important things we can do to prevent the spread of the virus," Bates said Saturday night in a statement.
CNN previously reported that Trump's agreement to don a mask in public was the result of heavy "pleading" by aides, who urged the President to set an example for his supporters by wearing a mask on the visit.
Masks have become a political flash point as some Americans argue the requirement infringes upon their civil liberties. But the US Centers for Disease Control and Prevention urges everyone to wear a "cloth face cover when they have to go out in public," noting that masks are critical in areas where social distancing is difficult to maintain since the coronavirus can spread between asymptomatic people and through respiratory droplets in the air.
Even after the federal government recommended Americans wear masks in places where social distancing is impossible, Trump declared he was unlikely to ever wear one himself. And even as some of his aides gently encouraged him to be seen following his own government's advice, Trump insisted wearing a mask would make him appear weak and give off the impression that he wasn't controlling the pandemic.
The President has also ridiculed those who have worn one publicly, like Biden. The White House insists that mask wearing isn't necessary for Trump since he and those around him are tested regularly for Covid-19.
During a May visit to a Ford plant in Michigan, Trump refused to wear a mask in view of the press, because he said he didn't want to give into media criticism and pressure.
This story has been updated with additional details.
CNN's Kelly Mena, Veronica Stracqualursi, Sarah Mucha, Jeremy Diamond, Kevin Liptak and Jason Hoffman contributed to this report.