Supporters of Bernie SandersBernie SandersSanders to join teachers, auto workers striking in Midwest Krystal Ball tears into 'Never Trump' Republicans 2020 Democrats defend climate priorities in MSNBC forum MORE expressed outrage and suspicion after reports of an email sent to Hillary ClintonHillary Diane Rodham ClintonMissing piece to the Ukraine puzzle: State Department's overture to Rudy Giuliani On The Money: Trump downplays urgency of China trade talks | Chinese negotiators cut US trip short in new setback | Trump sanctions Iran's national bank | Survey finds Pennsylvania, Wisconsin lost the most factory jobs in past year Meghan McCain, Ana Navarro get heated over whistleblower debate MORE supporters with an image labeled "secret win" surfaced shortly after The Associated Press said she had secured the Democratic presidential nomination.

The AP based its declaration on its own delegate count, including superdelegates. But Sanders supporters say that is unfair because the unbound party leaders could potentially switch their support at any time in the weeks leading up to the Democratic National Convention in July. 

Many Sanders supporters have voiced suspicions that Democratic Party leaders have rigged the primary against him to make sure Clinton wins the nomination.

Actor Tim Robbins, an outspoken Sanders supporter, blamed his loss in the New York primary on voter fraud, saying the “election is being stolen."