Donald Trump is spearheading his own defence amid his worst political crisis since entering the White House, claiming the world’s financial markets would crash and make everybody “very poor” if his critics sought to impeach him.

Two days after his former campaign manager was convicted of money laundering and tax evasion, and his one-time personal lawyer pleaded guilty to charges of violating campaign rules, the president made himself his own spokesman, economic forecaster and legal expert.

“If I ever got impeached, I think the market would crash, I think everybody would be very poor,” he told Fox News, in an interview that aired on Thursday morning. “You would see numbers that you wouldn’t believe.”

Both Mr Trump’s former lawyer, Michael Cohen, and ex-campaign manager, Paul Manafort, have yet to be sentenced, and Manafort faces a second trial on related changes.

While Manafort, or rather his lawyers, has yet commented on this week’s verdict, Cohen’s lawyer, Lanny Davis, suggested his client was prepared to cooperate with special counsel Robert Mueller’s ongoing probe into Russia’s alleged interference in the 2016 election. He said Cohen could about a “conspiracy to collude”.

“Mr Cohen has knowledge on certain subjects that should be of interest to the special counsel and is more than happy to tell the special counsel all that he knows,” said Mr Davis.

Supporters of the president have claimed Cohen was effectively forced “to flip” by Mr Mueller, given the prospect of a lengthy jail term, and the so-called fixer said earlier this summer that protecting his family – and not the president – had become his top priority.

Mr Trump, said to be furious that Cohen had told a New York court that his actions had been directed by the president, even suggested that such a process ought to be ended, because once defendants had flipped they “just make up lies”.

“For 30, 40 years I’ve been watching flippers. Everything’s wonderful and then they get 10 years in jail and they – they flip on whoever the next highest one is, or as high as you can go,” he said.

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“You know, I guess it says something like high crimes and all – I don’t know how you can impeach somebody who has done a great job.”

Asked as to how he would rate his presidency to date, Mr Trump referred to the US’s record bull market and his successful appointment of Justice Neil Gorsuch to the Supreme Court.

“I give myself an A+. I don’t think any president has ever done what I have done,” he said.

“We haven’t even been two years [in office]. Biggest tax cuts in history. Soon to be two unbelievable Supreme Court justices, I’m sure that Justice Kavanaugh will be approved. Justice Gorsuch has been a star.”

He added: “You look at all the things we have done with regulations, the economy is the best it has ever been in history. The only thing I’m doing badly in is the press doesn’t cover me fairly.”

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Mr Trump did not say if he would pardon Manafort, but expressed “great respect” for him and argued some of the charges “every consultant, every lobbyist in Washington probably does”.

Cohen, who said he would not seek a pardon from Mr Trump, pleaded guilty on Tuesday to eight charges, including campaign finance violations that he said he carried out in coordination with the then Republican presidential candidate. The Associated Press said behind closed doors, Mr Trump expressed worry and frustration that a man intimately familiar with his political, personal and business dealings for more than a decade had turned on him.

Cohen had said on Tuesday he secretly used shell companies to make payments used to silence former Playboy model Karen McDougal and adult-film actress Stormy Daniels for the purpose of influencing the 2016 election.

Mr Trump has insisted that he found out about the payments only after they were made, despite the release of a September 2016 taped conversation in which Mr Trump and Cohen can be heard discussing a deal to pay Ms McDougal for her story of a 2006 affair she says she had with Mr Trump.

Former George W Bush’s press secretary Ari Fleischer claimed the revelations that emerged in court this week may have been sordid, but did not meet the constitutional bar of “high crimes and misdemeanours”, required for impeachment.

“Having an affair and lying about it with a porn star and a Playboy bunny is not impeachable – it’s Donald Trump,” he said.

Mr Trump’s legal problems have made the upcoming midterm elections all the more significant. Republicans currently control both the Senate and the House of Representatives.

If they were to lose the house, as most analysts expect them to, it could open the way for impeachment proceedings against the president to begin. Analysts currently believe Republicans will likely retain control of the Senate, which would need to either confirm, or vote down, any impeachment motion from the lower chamber.

Meanwhile, South Africa’s government attacked Mr Trump after he tweeted that his administration would be looking into farm seizures and the “large scale killing of farmers” in the country. Critics said his comments appeared to be designed to stir up racial tension.

The government said Mr Trump’s tweet was based on false information and reflected a “narrow perception which only seeks to divide our nation and reminds us of our colonial past”. It was meeting with the US embassy as it sought to clarify the president’s remarks.