"I'm afraid the election's gonna be rigged, I have to be honest," Trump told the crowd.
While Trump has often questioned the integrity of the primary contests in both parties, his newest remarks seemed to begin laying groundwork for him to contest the Nov. 8 election results.
It was a line of attack that longtime Trump adviser Roger Stone pushed on a podcast with Breitbart's Milo Yiannopoulos that was posted online Friday. Stone suggested voter fraud is "widespread" and said if Hillary Clinton wins a state like Florida after polls show Trump in the lead, the election would be "illegitimate."
"If there’s voter fraud, this election will be illegitimate, the election of the winner will be illegitimate, we will have a constitutional crisis, widespread civil disobedience, and the government will no longer be the government," Stone said. He also promised a "bloodbath" if the Democrats attempt to "steal" the election.
Voter fraud is so statistically rare as to be virtually nonexistent, data has shown.