To judge the effectiveness of the special counsel’s Trump-Russia inquiry look no further than the reaction of those in its crosshairs

One measure of special counsel Robert Mueller’s prosecutorial success in 2018 is the list of former top Donald Trump aides brought to justice: Michael Cohen pleaded guilty, a jury convicted Paul Manafort, a judge berated Michael Flynn.

Another measure is the tally of new defendants that Mueller’s team charged (34), the number of new guilty pleas he netted (five) and the amount of money he clawed back through tax fraud cases ($48m).

Yet another measure might judge Mueller’s pace compared with previous independent prosecutors. “I would refer to it as a lightning pace,” said Barb McQuade, a University of Michigan law professor and former US attorney. “In a case of this complexity which has international implications, aspects relying on the intelligence community, complicated cyber components – to indict that many people that quickly is really impressive work.”

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But there’s perhaps a more powerful way to measure Mueller’s progress in his investigation into Russian interference in the 2016 US election and links between Moscow and the Trump campaign; that’s by noticing how the targets of his investigation have changed their postures over the course of 2018, from defiance to docility – or in the case of Trump himself, from defiance to extreme, hyperventilating defiance.

The distance Mueller has traveled over the last year can be measured in the orders of magnitude by which Trump’s criminal associates’ bombastic sense of their own impunity has been deflated, as the president’s attacks on the special counsel have grown increasingly shrill.

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Manafort went from tough-guy talk about “the battle to prove our innocence” to accepting a plea deal with Mueller, later broken. Cohen went from “taking a bullet” for Trump to telling Mueller everything.

Trump’s lead spokesman, Rudy Giuliani, has made a gradual transition in his defense of the president from “there was no collusion” to “collusion is not a crime”.

The slow, steady pressure from Mueller’s investigation has forced a group of fast-talkers accustomed to saying anything – “Lock her up!” – to fall momentarily dumb, or at least to modulate their speech.

And no public figure has undergone a more dramatic shift than Trump himself. Throughout 2018, Trump repeatedly erupted on the topic of Mueller, but three outbursts were notably impassioned, possibly indicating key achievements by Mueller – or areas where the president thought the special counsel was too close for comfort.

One came in April, after federal agents raided Cohen’s office and residences. One came in August, just before cooperation deals with the longtime Trump Organization executive Allen Weisselberg and longtime Trump friend David Pecker were announced. And one came after the election, when a slew of developments landed, from the exposure of Trump’s Moscow project to the sentencing of Cohen to prison to Flynn’s public dressing-down.

“It’s a disgrace, it’s frankly a real disgrace,” Trump said on camera after the Cohen raids. “It’s an attack on our country in a true sense. It’s an attack on what we all stand for.”

Trump was right to be concerned. Evidence collected in the raids appears to have cracked wide open a case involving hush payments by Trump to the porn star Stormy Daniels and former model Karen McDougal. Those payments have been assessed in court to be federal felonies. And recordings seized in the same raid appear to have spawned entire new fields of inquiry including an investigation of Trump’s inaugural committee.

Facebook Twitter Pinterest The president’s former lawyer Michael Cohen: the raid on his home and office in April may come to be seen as a watershed moment in the investigation. Photograph: Jeenah Moon/Reuters

Lisa K Griffin, law professor at Duke University, said the Cohen raid appeared to be a watershed moment in the investigation, for the fuel it gave to Mueller but also to separate US attorney’s offices.

“In hindsight it may appear that the most significant day in all of this was the day that federal agents executed search warrants on Michael Cohen’s office and home,” Griffin said, “because it continues to appear that there are many threads to both the southern district of New York and the special counsel’s investigation, that were generated by what they seized because of the longstanding relationship between Mr Cohen and the president.”

In prosecuting the hush payments, Mueller overcame an effort by Trump to hide one secret about how the 2016 election was won. But Mueller in 2018 continued to fill in the blanks of an even bigger secret, one that Trump tried with equal effort to suppress.

In February and again in July, Mueller unsealed indictments that described a coordinated Russian hacking and election-tampering effort conceived as early as 2014 and carried out using stolen US identities, camouflaged IP addresses and phishing scams, as well as physical spying inside the United States.

Trump had long questioned a Russian role in the election-relating hacking, and he kept it up after the second indictment was unveiled, when the US president found himself alongside the Russian president, Vladimir Putin, at a summit in Helsinki. “I have great confidence in my intelligence people,” Trump said, “but I will tell you that President Putin was extremely strong and powerful in his denial today.”

Yet it seemed that Mueller had hit his mark. Upon his return to the United States, Trump escalated his attacks on the special counsel, tweeting: “This is a terrible situation and Attorney General Jeff Sessions should stop this Rigged Witch Hunt right now, before it continues to stain our country any further.”

What followed was a bad August for Trump – and strong one for Mueller, who simultaneously on 21 August revealed Cohen’s guilty plea and saw a jury convict Manafort on eight fraud counts. Then Mueller unveiled the cooperation agreements with Pecker and Weisselberg, who together know more about Trump’s businesses and private affairs than perhaps anyone apart from Trump himself.

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In the continuing tug-of-war between the president and the prosecutor, the public appears to be siding with Mueller. A CNN-SSRS poll in early December found that respondents approved of the job Mueller was doing by a margin of 43-40, while Trump’s approval has been at least 10 points underwater in the poll since Mueller was appointed in May 2017. Trump had a 39-52 approval rating in December, the poll found.

In the year ahead, it appears that Flynn and Manafort will be sentenced, and further indictments against Trump-world figures are expected to be handed down. Mueller is expected to reveal whether he discovered evidence of cooperation between the Trump campaign and Russian operatives, and he might deliver a report on his investigation of alleged obstruction of justice by the president.

One year ago, the top question on the minds of many experienced observers was whether Trump would seek to fire Mueller. In the past seven weeks, the attorney general has been dismissed and the deputy attorney general, Rod Rosenstein, has been stripped of some of his power to oversee the special counsel.

But Mueller is still in place, on the threshold of 2019, which might be his biggest year yet.