Ron DeSantis has rejected Donald Trump's voter fraud claims in his first network television interview of the US presidential campaign, while warning Republicans to drop the scandal-plagued former president -- or risk losing in 2024.

The Florida governor, sitting a distant second behind Trump in Republican primary polling averages, said the last election had not been perfect, but he dismissed the frontrunner's false allegations of foul play by President Joe Biden's Democrats.

"Of course he lost. Of course. Joe Biden's the president," said DeSantis, who sat down with NBC on Sunday after spending two months avoiding the glare of mainstream broadcast audiences, in favor of mostly conservative cable and internet stations. NBC provided early excerpts of the interview, which is airing Monday.

The majority of Republican primary voters believe wrongly that Trump won the last election, according to polls, so bolstering the former president's false claims of fraud has become a litmus test for those hoping to rise in the party ranks.

The 44-year-old governor's remarks in the NBC interview were his clearest yet backing the legitimacy of the election, described as the "most secure in American history" by Trump's Cybersecurity and Infrastructure Security Agency.

DeSantis objected, however, to what he sees as an over-reliance in 2020 on mail-in voting, a practice Trump has falsely characterized as being susceptible to fraud but which is encouraged by the Republican Party and widely available in Florida.

The twice-impeached Trump has been indicted over his efforts to overturn the election that culminated in the January 6, 2021 insurrection at the US Capitol.

The case is the most serious of four criminal probes that have yielded dozens of felony charges, including allegations that the 77-year-old billionaire endangered national security by storing classified documents at his Mar-a-Lago beach resort in Florida.

DeSantis -- who was interviewed alongside his wife, Casey -- pulled his punches on Trump's legal woes, arguing that focusing too heavily on the former president's multiple prosecutions would spell defeat for Republicans.

"If the election is a referendum on Joe Biden's policies and the failures that we've seen, and we are presenting a positive vision for the future, we will win the presidency and we will have a chance to turn the country around," DeSantis said.

"If, on the other hand, the election is not about January 20, 2025, but January 6, 2021, or what document was left by the toilet at Mar-a-Lago, if it's a referendum on that, we are going to lose."