"Voter fraud is real and it is absolutely happening every single day. And the Democrats don't care," the president's son told host Jesse Watters during an appearance on Fox News' "Watters' World." "And the media wants to ignore it."
Trump, an executive vice president of the Trump Organization, slammed Democrats for trying to push the narrative that voter fraud involving mail-in ballots doesn't exist.
President Trump tweeted last Sunday that due to the "process" voters must go through to obtain an absentee ballot, such voting is safer than general mail-in balloting — and he pointed to a voter-fraud scandal in New Jersey in May as evidence that universal mail-in voting would cause widespread problems.
Watters then asked Trump about Twitter, alleging the microblogging site was pushing a narrative in favor of mail-in voting, something Trump said was "dangerous."
"You and I and every other conservative out there we've known what has been happening the whole time," Trump said. "I mean, every single kind of outspoken conservative has been shadow-banned behind the, behind the scenes. There's just no question."
Trump also said any Twitter censorship against conservatives would backfire on Democrats because of Americans' love for free speech.
"It's going to cost them the election because the one thing that Republicans, the one thing that Americans don't want to have happen to them is to have their free speech silenced, right?" Trump said. "We have the First Amendment protection for a reason. Americans fundamentally -- it's ingrained in their DNA, believe in having free speech.
"And I'm telling you, it's gonna backfire on them. Do not take that ability away from Americans. And there is no better way, there is no more surefire way to get Americans out to the polls to vote for Donald Trump to stifle their free speech."
Fox News' Tyler Olson contributed to this report.