Thank you so much, I am much obliged to you for this.
On looking through the alternatives you offer I am particularly attracted to 'election riggers of Russia' since I am told that вброс here stands for вброс избира́тельных бюллете́ней or ballot stuffing, lit. the throwing-in (i.e to the urn) of (several) voting papers.
Since the allegation is that the ruling party falsified the vote, the picture I get from единовбро́сы is one of united/monolithic (едино-) ballot stuffers (вбро́сы).
Reference:
http://ru.wikipedia.org/wiki/Вброс_бюллетеней
The translation workplace 
peer agreement (net): +1
