This is not likely doable for a non-USN/non-GE who isn't really familiar with the airport and has any checked luggage.
But, unless it's the last flight of the night, it's not world-ending. In addition, it's only a 2-1/2 hour train ride to WAS, so there are backups.
If this is an inexperienced traveler or someone with any language barriers, I would simply change to the next EWR-DCA and play this safer.