Donald Trump's daughter Ivanka and her husband Jared Kushner are Washington's ultimate power couple after the President and First Lady, influential through both bloodline and their official senior adviser roles.

But the pair are not universally popular in the White House, and are at loggerheads with exiting chief of staff John Kelly.

Mr Kelly joked the couple was "playing government" and thought they did not have to follow the rules, according to the Washington Post. They should never have been brought into the White House, he added.

The chief of staff is reportedly "furious" with Ms Trump and Mr Kushner, according to the New York Times. One senior administration official said Mr Kelly deliberately left written notes about the couple and things they had done or requested on his desk in view of his staff.

The couple appears on a list of 16 Trump associates named by US media as having had contact with Russia during his 2016 presidential campaign or transition.

The damning list includes Michael Cohen, Michael Flynn and Paul Manafort - who are awaiting sentencing on criminal charges.

Each of them spoke with Russians in person or via phone calls, text messages and video chat.

The US President and his senior staff repeatedly denied any contact with Russia during the campaign. Mr Trump has now admitted there may have been business talks, but insists that does not amount to the "collusion" in Russian election meddling that Special Counsel Robert Mueller is investigating.

On Friday, Mr Mueller released a series of filings that linked Mr Trump to criminal activity - trading political advantage for a lucrative business opportunity. He could face impeachment or even jail time over it.

"It is no longer journalistically sound to report on the Trump investigation as if it is a matter that may, or may not, yield damning information about the President," wrote Adam Davidson in the New Yorker - saying that it already has.

But Mr Trump refuses to acknowledge this, posting a fresh barrage of tweets on Monday, in which he referred to his former lawyer Mr Cohen's $180,000 hush payment to Stephanie Clifford, aka porn star Stormy Daniels, as "a simple private transaction".

Jerrold Nadler, a New York Democrat set to take over the House Judiciary Committee, said this would be an "impeachable offence".

Mr Mueller's filings claimed Mr Cohen "acted with the intent to influence the 2016 presidential election" at the direction of Mr Trump when he paid women to not go public about their alleged affairs with the presidential candidate.

Mr Trump argued the payments, which he initially denied knowing about, were not campaign contributions because they came from his own funds. Federal law requires disclosure of payments made "for the purposes of influencing" an election.

The filings also revealed Mr Cohen spoke about Mr Trump's campaign with a Russian in November 2015 and lied to Congress over an ongoing Trump Tower Moscow deal, while former campaign chairman Mr Manafort lied about his contact with a Russian official linked to Democrat email hacking.

Mr Manafort, who pleaded guilty to conspiracy in September, will face a court hearing on Tuesday afternoon.

"What is obvious is that, despite Trump's denials, he and his campaign were involved in repeated, serious efforts to develop deep connections to Vladimir Putin's regime from the very beginning of Trump's run for the presidency," wrote James Risen in The Intercept.

Meanwhile, Mr Trump also lost Mr Kelly's expected successor as White House chief of staff, Nick Ayers, who announced on Sunday he would instead be resigning. Two sources told CNN Mr Ayers had left because of Melania Trump, who has become increasingly vocal in West Wing staff matters.

The President now urgently needs to work out who to install in the chief of staff job, according to reports, and is reportedly considering chairman of the ultraconservative House Freedom Caucus Mark Meadows.

Other potential names included Treasury secretary Steven Mnuchin, budget director Mick Mulvaney, former deputy campaign manager David Bossie, US trade representative Robert Lighthizer and New Jersey governor Chris Christie, who as an ex-government lawyer could help Mr Trump in an impeachment fight.

On Sunday, the President tweeted that the "Fake News Media" was "totally out of its mind" and the "enemy of the people", that former FBI director James Comey's testimony was "untruthful" and that the "whole deal is a Rigged Fraud headed up by dishonest people who would do anything so that I could not become President".

But with Mr Mueller cracking down, the loss of yet another staff member is bad news for Mr Trump. The Democrats will take the majority in the House of Representatives in the new year, and are planning promised multiple investigations into the President's finances - again involving his family members.

"The President has now stepped into the same territory that ultimately led to President Nixon resigning the office," Senator Chris Murphy told the US ABC on Sunday. "President Nixon was an unindicted co-conspirator ... certainly a different set of facts."

With the country set to head into recession, Mr Trump needs all the support he can find before 2020 arrives.

California Democrat Adam Schiff said there was a "very real prospect" he could be indicted on the day he leaves office and the "next president could have to decide whether to pardon him".

And his tainted gang of 16 may soon no longer be able to help him.

THE TRUMP 16

1. Former Trump campaign chairman Paul Manafort

2. Former Trump deputy campaign chairman Rick Gates

3. Former national security adviser Michael Flynn

4. White House senior adviser Jared Kushner

5. White House senior adviser Ivanka Trump

6. Trump Organisation executive Donald Trump Jr.

7. Former Trump lawyer Michael Cohen

8. Former Attorney-General Jeff Sessions

9. Trump campaign adviser George Papadopoulos

10. Former Trump campaign adviser Carter Page

11. Former Trump campaign aide Roger Stone

12. Trump associate Erik Prince

13. Trump campaign adviser JD Gordon

14. White House official Avi Berkowitz

15. Former Trump campaign aide Michael Caputo

16. Trump business associate Felix Sater