Donald Trump promised to deliver 'really big news' during a Thursday night speech, where he is expected to uncover bombshell evidence of voter fraud.

The address will reveal declassified intelligence from investigations into US elections and alleged vulnerabilities in voting machines, a White House official told Reuters. 

Left-wing Congresswoman Alexandria Ocasio-Cortez, meanwhile, said networks have an 'obligation' not to air the speech if he intends to mislead America. 

Trump would not release specifics when asked about the speech on Tuesday but did hint that it could be a blockbuster.  

'I'd rather save it, it will concern [election machines]. It's really big news. It's really, really big news,' he said in the Oval Office.  

'Our country has to shape up. What we're going to be talking about Thursday, it doesn't get bigger.' 

The President could ‌also use his televised speech at 9pm ET to press his debunked claim that he lost his 2020 reelection to Joe Biden due to massive fraud.

Numerous courts, ballot audits and his first-term Justice Department found no evidence of such fraud, including vote-machine rigging. 

The federal cybersecurity watchdog joined other federal, state and local officials in declaring the vote 'the most secure in American history.'

Asked ​if his speech would address election machine integrity, Trump told reporters on Tuesday, 'It will concern that subject' among others, but gave no details.

Propelled by Trump's ​repeated claims that US elections are 'rigged,' the administration has for over a year sought to increase federal oversight of election administration and ⁠reshape the way Americans vote — an effort that legal experts say would take power away from states in violation of the US Constitution.

With Republican control of Congress at ​stake in the November midterm elections, Democrats and some election security experts have expressed concerns that the Trump administration plans to interfere in those contests.

Ocasio-Cortez suggested the networks shouldn't even bother to air it.  

'He's basically doing a made-for-TV broadcast about election fraud and conspiracy theories,' she told MeidasTouch.

'I don't think we should be contributing to the platforming of lies about our elections. Many news outlets oftentimes may receive transcripts [in advance], and I think we have an ethical obligation not to air things that undermine our elections that are not rooted in evidence and in fact.'

Meanwhile, Georgia Senator Jon Ossoff spoke to MS NOW, suggesting he had heard rumors that Trump might try and declare his and fellow Georgia Democrat Raphael Warnock's victories 'illegitimate.'

'I expect him to use whatever he puts out there on Thursday as a pretext, either for some attempted unconstitutional use of federal power to interfere in the election, or to give his proxies and loyalists in state and local jurisdictions some cover for whatever they might attempt or to lay the groundwork for challenging the result.'

Ossoff slammed the President for focusing on this when he had so many other key issues to deal with. 

'You've got the American public broadly furious with the president for war and tariffs and health care cuts that are making everything more expensive,' Ossoff said. 

'So now he's pivoting from ballroom obsession to election conspiracy theory obsession, this is politically disastrous for Republicans in Georgia.' 

By casting the 2020 election ​as illegitimate, Trump is laying the groundwork to challenge Republican losses and undermine Democrats if they win back power in Congress in November, multiple election experts have said.

An administration official, who discussed the plans on condition of anonymity, said on Monday that Trump will discuss in his speech national elections and what White House officials view as voting machine flaws that could permit foreign cyber intrusion.

The administration official said Trump ​would discuss newly declassified intelligence related to 2020.

Election officials say they are confident that machines are adequately secure and ​no evidence has been found of foreign intrusions that changed results of past elections.

A forensic analysis submitted last year by Mojave Research, a contractor hired by former director of national intelligence Tulsi Gabbard, ‌found flaws ⁠in voting machines seized in Puerto Rico but no evidence of hacking.

Gabbard, whose resignation was effective last month, also produced her own report that outlined significant vulnerabilities in voting machines and further safeguards, such as updating their software, that could be implemented, three sources familiar with the matter said.

The White House, however, has delayed releasing the report, and Trump has persisted in trying to prove that his 2020 defeat was due to fraud.

He appointed Bill Pulte, director of the federal mortgage regulator, last month as Gabbard's interim replacement and ​said he had authorized Pulte to declassify ​documents related to the 2020 vote. 

The White House also recently formed a task force to investigate elements of the 2020 election, three sources familiar with the matter said on condition of anonymity.

One source said journalist John Solomon, a former Fox News contributor, is working on the effort.

Solomon, the ​source said, has requested access to files related to an analysis that dissented from a US intelligence assessment in 2021 ​that found no indications ⁠that a foreign actor had tried or succeeded in altering 'any technical aspect' of the 2020 vote.

The unclassified version of the assessment judged that Russian President Vladimir Putin authorized parts of his government to conduct influence operations aimed at boosting the vote for Trump and undermining public confidence in the US electoral process.

China considered conducting influence operations designed to change the election ⁠outcome but decided ​against doing so, while Iran pursued a 'multi-pronged' covert influence campaign to undercut Trump's candidacy, the assessment said.

The ​report was drafted by the National Intelligence Council, the top body of US intelligence analysts, along with the CIA, the Department of Homeland Security, the FBI, the State Department's intelligence bureau and the National Security Agency.