While some of those protesting are everyday Trump supporters, there are also some less savoury elements at the rally, including extremist far-right group The Proud Boys.
As the crowd gathered, McEnany tweeted screen grabs from Fox News and said the march was "AMAZING!"
"More than one MILLION marchers for President Trump descend on swamp in support".
But was it really a million people? While there was certainly a crowd over one or two city blocks, it seemed to be a lot fewer people than a million. Perhaps a few thousand would be more accurate.
McEnany's throwaway "million" line led to some ribbing.
"Big Sean Spicer energy here," said Sawyer Hackett who was a staffer in the Obama administration referring to one of McEnany's predecessors who falsely said Trump's 2017 inauguration attracted the biggest crowd of such an event in history.
Others pointed out that when you zoomed out, the crowd thinned out very quickly.
Journalist Max Burns said: "The inability to tell the difference between a Thousand MAGA March and a Million MAGA March is another reason Trump lost the counts in GA, PA, MI, AZ, NV and WI."
CNN said there were not "remotely" one million people at the Million MAGA March.
Trump doubles down on "massive" march claims
US President Donald Trump is railing at suggestions the "Million MAGA March" in Washington DC isn't that massive.
The protest goes under various names. Those in attendance are urging Trump not to concede and backing so-far unproven claims of vote rigging.
TV networks have estimated that far from a million people – which was always going to be a tall order – there are several thousand tops.
But Trump has said, you guessed it, "FAKE NEWS".
He tweeted a snap from Dan Scavino, the White House deputy communications director, showing what appeared to me a much fuller crowd.
"FoxNews and the Fake News Networks aren't showing these massive gatherings. Instead they have their reporters standing in almost empty streets. We now have SUPPRESSION BY THE PRESS. MAGA!"
Fox News has said the crowds at the march are "huge".
The network said "tens of thousands" of people were in attendance.
Most TV stations have said the protest is large and has attracted "thousands".
But that is still less than the "million" White House Press Secretary Kayleigh McEnany claimed were protesting.
Some TV stations have aired zoomed-out images which appear to show the march covering one to two blocks of the capital.
