Does the team have an official Twitter hashtag? Based on a review of the six Twitter accounts associated with the team that I'm aware of there is no consistency on whether #Nats or #Nationals is used. This leads to mixed use by the local and national media. I have the #Nats search bookmarked as it seems to get the most use, but that means I miss stuff posted using #Nationals. In both cases there is often a good deal of concurrent usage of the tags, #nationals gets used quite often for a week at a time when there are national competitions, and #nats is a tweebonics term. I'd suggest creating a new official hashtag for use by the team's accounts and suggested for use by the media and fans, something that would be unique for the team such as #NatsBB, #DCNats, or even #Nats69.
Official Team Accounts:
@Nationals - mostly #Nats one #Nationals
@NatMobile - neither
@ScreechtheEagle - a mix of both
@NationalsPR - a mix of both
@NatsTix - #Nats
@Teddy26Nats - mostly #Nats some #Nationals
Media Accounts:
@MASNNationals - mostly #Nationals some #Nats
@NatsJournal - a mix of both
@MarkZuckerman - mostly #Nats some #Nationals