More than a dozen times in the past seven days, President Donald Trump has alleged, contrary to evidence, that the recount of Florida's elections for governor and the U.S. Senate has been marred by fraud.

"Many ballots are missing or forged," he tweeted on Monday. "Ballots massively infected."

The unsubstantiated allegations could help Trump bolster a narrative that appeals to his core supporters ahead of his expected 2020 bid for a second term — that of an aggrieved president at risk of being cheated by what he often decries at rallies as an unfair system.