The special counsel investigation into Russian meddling and possible collusion is notoriously leak-proof but it could soon touch Trump directly or members of his family

After two years of the Donald Trump presidency, the national stores of civic goodwill are depleted. That could make for a testy 2019, because it appears that the country’s defining political tensions are about to break into open clashes.

One field of battle will be Congress, where Democrats say they will use their control of the House of Representatives to mount investigations of Trump and his coterie. Another will be the campaign trail, where Democrats (and maybe some Republicans) will begin to compete to replace Trump.

But perhaps overshadowing them all is special counsel Robert Mueller’s investigation into Russian interference in the 2016 US election, and links between the Trump campaign and Moscow.

Mueller is expected to advance significant new aspects of his investigation, which could end up targeting Trump himself in a very public way in the new year, according to legal experts and observers.

Analysts interviewed by the Guardian uniformly warned that Mueller’s velocity and vector are basically unknowable, because his team does not leak private information, while salient public information, such as Mueller’s willingness to move to the sentencing phase for cooperative convicts such as Michael Flynn, is open to interpretation.

But the broadest possible question about what the next year might hold in store for Mueller pertains to his core investigation of alleged collusion between the Trump campaign and Russia and obstruction of justice by the president, analysts said.

“I think the biggest question is, is he going to present evidence that Trump committed crimes?” said Alex Whiting, a Harvard law professor and former prosecutor on the international criminal court. “Either obstruction of justice or collusion. He wouldn’t bring an indictment because justice department policy won’t permit it. But whatever evidence would be handed off, I think, to the Congress, and it will have to be considered.

“That’s as big as it gets. I think that’s really – that’s the ultimate question.”

A basic obscurity and air of secrecy still attend Mueller’s work. For all the major developments in the Mueller investigation in 2018 – from the April raid on former Trump fixer Michael Cohen’s home to the fiery Flynn sentencing hearing earlier this month – the public gained a relatively limited view on the progress of Mueller’s core investigation of election tampering and potential obstruction.

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A Mueller memo describing Flynn’s “valuable” cooperation was almost entirely redacted in sections describing Russia-related matters. Likewise, a Cohen memo was adamantly non-specific in its description of “core” investigative matters that Cohen helped with.

One of the most revealing Mueller documents to emerge was a draft plea agreement with the conspiracy theorist Jerome Corsi revealing that Mueller alleged that Corsi helped Trump political adviser Roger Stone communicate with WikiLeaks, which served during the election as a Russian cutout.

“For now, he appears to be building charges against Corsi and Stone,” former US attorney Renato Mariotti said of Mueller.

If Trump himself would be the biggest target Mueller might approach in 2019, and Corsi or Stone would be lower-level, Mueller might also target someone just short of the president, such as Trump’s son, Donald Trump Jr, or his son-in-law, Jared Kushner, analysts said. Both men appear to be legally exposed to charges of making false statements either to investigators (as Flynn did) or to Congress (as Cohen did).

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Barb McQuade, a University of Michigan law professor and former US attorney, pointed to Mueller’s description of Cohen’s cooperation and noted that Cohen had “described the circumstances of preparing and circulating his response to the congressional inquiries” – a response he later admitted was false.

“That suggests there were others who were trying to get their story straight,” said McQuade. “And I imagine that that would be an area that Mueller would look at, to say: ‘Well, Michael Cohen told a lie. Did anyone else tell the same lie?’

Facebook Twitter Pinterest Michael Cohen ‘described the circumstances of preparing and circulating his response to the congressional inquiries’, Mueller wrote. Photograph: Xinhua/Barcroft Images

“And if they did tell that lie, number one, there are going to be charges against them for lying to Congress but, number two, why did they lie?

“People tend to lie under a situation as serious as that only if they believe that the truth would be worse. And so if they’re lying about the Trump tower Moscow, what truth about that is worse?”

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Major incidents before or after the last US presidential election could emerge as focal points for Mueller in the new year. The special counsel might reveal new evidence about the circumstances surrounding a June 2016 meeting at Trump Tower, or a February 2017 meeting between Trump and Comey, at which Comey said that Trump encouraged him to drop an investigation of Flynn.

Further criminal charges might emerge in the case of hush payments made to the porn actor Stormy Daniels and former Playboy model Karen McDougal, or new details might emerge of projects or prospective projects advanced by Trump and his family in Moscow or the Middle East. In the background would be questions about the nature of the Trump campaign’s relationships at the time with any foreign backers.

Foreign countries and nationals are not supposed to be involved in US campaigns or elections.

“We all at this moment know very little about where Robert Mueller’s investigation will lead, because it has been so leak-free and they have been so careful about keeping their cards very close to the vest, and admirably so,” said Lisa K Griffin, a law professor at Duke University with a focus on federal criminal justice policy.

“I don’t think anyone knows, and I think most of the conjecture about it has been wishful thinking in both directions.”

Whiting said: “Trump has tried repeatedly to minimized this investigation, to delegitimize it, to dismiss it, and that hasn’t worked and it’s not going to work.

“I think this investigation and the consequences are going to be significant and they’re here to stay, and there’s nothing he can do about it.”