Attention will turn to a courthouse just south of Washington DC tonight as the first trial of a Trump campaign official gets underway.

Paul Manafort, Donald Trump's former campaign director, is facing two separate trials for a range of financial crimes, as well as conspiracy and perjury charges.

None of the alleged crimes relate to the Trump campaign, but this is the first trial stemming from charges brought by Robert Mueller, the special counsel investigating Russia's interference in that election campaign.

Podcast Russia If You're Listening Paul Manafort: The dictator's fixer In four years Paul Manafort went from making millions of dollars in Ukraine, to running the Trump campaign, to jail. How did this man get landed with over a dozen federal indictments? About

About Subscribe

Subscribe RSS Space to play or pause, M to mute, left and right arrows to seek, up and down arrows for volume. Listen More great ABC podcasts

So, who is Paul Manafort, what is he charged with, and why does it matter to the US President?

Who is Paul Manafort?

Mr Manafort, a Republican political operative with decades of experience, was head of the Trump presidential campaign for several months in 2016.

"I work directly for the boss... I have one man whose voice is louder than everybody else's," he told CNN.

Then campaign manager Paul Manafort (centre) with Donald Trump and his daughter, Ivanka. (2016) ( Reuters: Rick Wilking )

He was in charge of the campaign when stories started coming out about potential connections between Donald Trump, his campaign, and Russia. He has said those stories were "absurd".

Mr Manafort left the campaign when ties were discovered between him and the Putin-aligned former Ukranian president Viktor Yanukovych.

Before he joined the Trump campaign, Mr Manafort worked for Mr Yanukovych for nearly a decade, and had become incredibly wealthy.

He'd been paid millions of dollars to act as Mr Yanukovych's political consultant, and had also run up big debts to the Russian oligarch who got him that job.

According to the US Justice Department, Mr Manafort spent that time bringing the cash back into the US without paying tax on it.

When Mr Yanukovych was run out of the country in a revolution in 2014, Mr Manafort was in a bind.

He was still in debt, and his main source of funds had dried up. So he engaged in a number of activities to raise money which may not have been strictly legal.

What are the charges against him?

A year after he left the Trump campaign, Mr Manafort was put under house arrest by Mr Mueller.

Tonight, Mr Manafort will face trial for some of the activities he undertook in 2015 to try and raise money to pay off his debts.

"The Government will try to allege that these are straightforward fraud committed by Manafort," said US law expert, Professor Sandeep Gopalan, about the charges in the first of the two trials.

Mr Manafort is charged with concealing income that he derived from offshore sources, depriving the government of tax income, and lying to the banks to obtain loans, Professor Gopalan said.

When talking to the tax office, he said he wasn't earning very much money at all. But when talking to banks, he vastly overstated his income to try and secure large loans.

"In regards to the bank, he's saying that he needs a loan because he needs to make certain real estate acquisitions, etc.

"And there, his statements of income are actually not factually correct," Professor Gopalan said.

The prosecution alleges that Mr Manafort secured a large loan from a small bank in Chicago in exchange for a promise that the bank's owner Stephen Calk would become the Secretary of the US Army.

"Mr Calk was successful in getting a job in the actual campaign, but was unsuccessful in getting a job in the administration itself," Professor Gopolan said.

Mr Calk was apparently taken in by this, and went so far as to call the Pentagon and ask for briefing materials so he could prepare for his new job running the US Army.

Loading...

"Allegedly he and a source who's alleged to be close to the Kremlin tried to elicit perjury from some of the parties who had knowledge of these transactions as it relates to Ukraine," Professor Gopolan said.

That was enough to get Mr Manafort tossed into jail, where he's been for the better part of a year. But he wasn't happy with the location of that jail.

"Once he gets transferred into this high security prison — it's a VIP facility — once he's there, his lawyers file a motion that they're having to spend a lot of time travelling to this place two hours outside to meet with their client, which of course interferes with their defence," Professor Gopolan said.

"They don't ask for a remedy; they basically say he shouldn't be put in this place because it interferes with his defence.

"And in response to that, Judge Ellis, the presiding judge in the trial in Alexandria, says, okay, if that's the case, we'll put him in jail in Alexandria.

"So they moved him to what is known as the Alexandria detention facility, which is known to be quite harsh and the conditions are not very good; so that's where he is now."

Sorry, this video has expired Manafort, Gates arrive at court to ask for release

How might Trump respond?

The Trump administration is paying very close attention to this.

The President's lawyer, Rudy Giuliani, has publicly suggested that at some point in the future, a presidential pardon may be on the way for Mr Manafort.

"When it's over — hey, he's the President of the United States, he retains his pardon power, nobody's taking that away from him," Mr Giuliani has said.

So why would the President be considering pardoning Mr Manafort, considering this trial has nothing to do with the Trump family or the campaign? The presiding judge has already offered an opinion.

"Judge Ellis's remarks to Mueller — you're not really interested in Manafort, are you?

"And what you're doing here in bringing these tax and bank fraud charges is piling on the pressure on this 70-year-old guy in the hope that he'll flip on Trump," Professor Gopolan said.

The judge in Paul Manafort's trial has already offered an opinion on the real reason Mueller is bringing the charges against Manafort. ( Reuters/AP )

So now the heat is on — will Mr Manafort flip and turn state's witness against the President, which is what Mr Mueller wants; or will President Trump pardon him, which is what Mr Manafort wants?

Professor Gopalan said the pressure was really on Mr Manafort at the moment.

"It seems like a pretty straightforward case where Manafort is sunk. And if that indeed is the case, he is looking at upwards of anywhere from 10 to 15 years, if not more, in jail.

"That's a lot for somebody to stare at and not to flip.

For that reason, Professor Gopalan said, the President's team was very, very focused on this case, even though at the moment it has nothing to do with Russia.