Allegations that a union privileged a more powerful faction within the union, together with a showing of deceptive actions can state a claim for breach of the duty of fair representation.
http://media.ca7.uscourts.gov/cgi-bin/rssExec.pl?Submit=Display&Path=Y2018/D08-13/C:17-1438:J:Ripple:aut:T:fnOp:N:2201507:S:0
Since 2011. An occasional commonplacing of the U.S. Circuit Courts of Appeal.
Neither an authoritative statement of the law nor legal advice. Quick work.