Top aides to Donald Trump sought Sunday to turn the tables on Democrats pushing for his impeachment, insisting the president was the true “whistleblower” in pushing Ukraine to investigate the son of rival Joe Biden for corruption.

Trump's Republican allies have closed ranks as he battles the deepest crisis of his presidency, flatly denying he abused his power and seeking to discredit the anonymous whistleblower who exposed the scandal.

“The president of the United States is the whistleblower,” Trump advisor Stephen Miller told “Fox News Sunday.”

“This individual is a saboteur trying to undermine a democratically elected government,” he said. “Getting to the bottom of a corruption scandal in Ukraine is in the American national interest.”

Read: The story behind Joe Biden’s son, Ukraine and Trump’s claims

Trump's personal lawyer Rudy Giuliani — who has emerged as his point man in the Ukraine scandal — led the charge along with Miller in a series of combative talk show appearances Sunday morning.

Brandishing what he said were affidavits incriminating Biden's son Hunter over his work at a Ukrainian company, Giuliani said Trump was duty bound to raise the issue with Kiev.

“If he hadn't asked them to investigate Biden, he would have violated the constitution,” Giuliani told ABC's “This Week.” “This is not about getting Joe Biden in trouble, this is about proving that Donald Trump was framed by the Democrats.”

Democratic 'savages'

The Democratic-led House of Representatives launched an official impeachment inquiry this week accusing Trump of a “mafia-like shakedown” of Ukrainian President Volodymyr Zelensky aimed at damaging his potential White House challenger in 2020.

Trump and his allies claim Biden, as Barack Obama's vice president, pressured Kiev to fire the country's top prosecutor to protect his son Hunter, who sat on the board of a gas company, Burisma Holdings, that was accused of corrupt practices.

Despite the questionable optics, those allegations have largely been debunked and there has been no evidence of illegal conduct or wrongdoing in Ukraine by the Bidens.

But a transcript of the July 25 call shows Trump pushing for Kiev to revisit the allegations, saying both Giuliani and US Attorney General Bill Barr would be in touch on the matter.

For Democrats, the call amounted to a smoking gun, leading Speaker Nancy Pelosi to finally approve an impeachment process she opposed as a risky distraction in the run-up to 2020 elections.

Trump insists he did nothing wrong, denouncing a new “witch hunt” against him.

Addressing his 65 million Twitter followers over the weekend, Trump assailed Democrats as “savages” and called for lawmaker Adam Schiff, who is leading the impeachment probe, to resign.

Whistleblower to testify 'very soon'

Democrats have charged aggressively into the impeachment probe, ordering Secretary of State Mike Pompeo to turn over Ukraine-related documents and scheduling witness testimony.

Appearing on NBC's “Meet the Press,” Schiff said he was “urgently” investigating all aspects of the Ukraine affair, including whether Trump withheld millions of dollars in aid as leverage.

The House Intelligence Committee chairman said he expected the White House to “fight us tooth and nail,” but warned that stonewalling would constitute obstruction of justice.

Asked if he planned to cooperate with Schiff's probe, Giuliani equivocated, saying he would only testify if asked to do so by the president.

Schiff said he had yet to decide whether to call on Giuliani.

But he did say he expected to hear testimony from the whistleblower “very soon” — and that all precautions were being taken to protect their identity.

Democrats have said articles of impeachment — formal charges — against Trump could be completed in as soon as a month and then swiftly voted on in the House, where the party has a majority.

Polls suggest public support is growing for the impeachment inquiry, with a new CBS survey showing 55 per cent of Americans — and nine in 10 Democrats — approve.

A separate ABC News/Ipsos poll showed two-thirds of Americans judged Trump's call to Zelensky to be a “serious issue.” But even if impeachment is approved in the House, Trump's trial would take place in the Senate — where, for the moment, he appears able to count on a Republican majority to prevent conviction.

One of Trump's most outspoken Senate defenders, Lindsey Graham, hammered home the party line on CBS's “Face the Nation.” “I have zero problems with this phone call. There is no quid pro quo here,” he said, pivoting to demand that somebody “look at whether or not Joe Biden had the prosecutor fired in an improper way.”

Between Saturday night and Sunday morning, the president retweeted dozens of video clips from Republican allies including Graham defending his conduct — while warning his supporters that “our country is at stake like never before. “