They perfected this tatic during the 2008 Democrat Senatorial/District caucuses in Texas (I witnessed it during Operation Chaos - long story.) It's their favorite tactic to use in those areas where they don't have corrupt election officials in their pockets.
They challeged so many delegates at the caucus that it would have taken us more than 24 hours to review and vote on each challenge. So, they got the Clinton legal team to give up 50% of the challenged delegates. (Obama's legal team likewise gave up 50% of their challenged delegates, but since Clinton didn't challenge very many of Obama's, they weren't really giving up a large number like Clinton was.
And because of other tactics I've described at length here previously, the alternate delegates who took the spots of challenged Clinton delegates were Obama alternate delegates. Believe me, they know how to use legal challenges to perpetuate fraud.
Josef Stalin said, “The man who votes decides nothing...The man who counts the votes decides everything...”