Judging by the snowballers total lack of respect for the law and authority I'm going to take a wild guess here and say that all or an overwhelming majority of these people are Obama voters.
DC chief slams officer over gun at snowball fight (AP/Yahoo News)
"DC Cop Waves Gun at Snowball Fight!" Sorry. I'm siding with the cop. (Althouse)
UPDATE: Looks like it wasn't an impromptu snowball fight after all. It appears to have been some sort of organized protest.