Donald Trump said he's worried the general election will be rigged against him during a campaign stop Monday afternoon.

The GOP nominee said he could relate with Democratic runner-up Bernie Sanders—identifying him as a fellow politician wronged by the system—when the Vermont senator yielded to Hillary Clinton last week in Philadelphia.

"Poor Bernie, he looked so upset. You know what? He made a mistake. He shouldn't have made a deal. He lost, he lost. First of all, it was rigged. And I'm afraid the election's gonna be rigged. I have to be honest, because I think my side was rigged," Trump said at a campaign stop in Ohio. "If I didn't win by massive landslides—I mean, think of what we won in New York, in Indiana, California, 78 percent—that's with other people in the race!"

Trump had actually been the only candidate in the Republican field for a month by the time the California primary arrived in June. But he plowed through 16 competitors en route to his party's nod for the White House in the months before then, a run he said took "guts" and cost him a relatively easier lifestyle.

"This started on June 16 of last year, and I said, wow, let's go do it. Takes guts to do this, believe me. And everybody said—no, it takes guts. I could be having a very nice life right now. I don't have to be with you people ranting and raving, right? Could have a very nice life. But it takes guts," he said.

Trump said Friday that Clinton and the Democratic party were trying to "rig" the election debate calendar by pitting two of the three events against prime-time NFL games. The preliminary dates have been in place since September.