In addition to investigating Russia's interference in the 2016 election, the special counsel Robert Mueller is scrutinizing dozens of contacts between President Donald Trump's campaign and Russia.

Trump and his surrogates have offered multiple, at times contradictory, explanations for those contacts.

Over time, they have claimed the campaign never communicated with Russia, that the contacts did not amount to collusion, and that even if they did, collusion is not a crime.

The special counsel Robert Mueller's investigation into Russia's interference in the 2016 election has so far indicted 34 people and three Russian companies, flipped five cooperating witnesses, secured one conviction in court, and seized up to $46 million in assets.

In December, Michael Cohen, President Donald Trump's former lawyer and "fixer," pleaded guilty and entered into a cooperation agreement with Mueller's team, sitting for at least 70 hours of interviews. And a series of new court filings has shed more light on the extent of Paul Manafort's contacts with Russian-linked individuals.

Since last May, Mueller has been investigating not only Russia's election meddling, but also whether the Trump campaign colluded with Moscow to tilt the race in Trump's favor.

The central thread in the probe focuses on the complex linkage of contacts between the Trump campaign and Russian individuals and entities.

Over time, Trump and his surrogates have had multiple, often contradictory, explanations for those contacts. Here's how their explanations have evolved between December 2016 and today.

November 2016: There was no contact with Russians

President Vladimir Putin directed the interference, US intelligence agencies have concluded. Thomas Kronsteiner / Getty Images

In the days immediately following the election, Russian president Vladimir Putin's spokesman Dmitry Peskov and a top Russian diplomat told the Associated Press the Russian government maintained "normal" contacts on matters of foreign affairs with both the Trump and Clinton campaigns.

Hope Hicks, then a campaign spokeswoman, categorically denied at the time that any such contacts had taken place.

"It never happened," she told the AP. "There was no communication between the campaign and any foreign entity during the campaign."

But subsequent reporting has now revealed at least 101 known points of contact between Trump campaign aides and Russia-linked individuals or entities.

Those include communications with Sergei Kislyak, Russia's former ambassador to the US; multiple powerful oligarchs closely aligned with Putin; and Russian intelligence officers who were involved in hacking then-Democratic nominee Hillary Clinton's campaign and the Democratic National Committee. The officers disseminated the stolen emails via WikiLeaks to influence the election, Mueller has charged.

Read more: Grading the Steele dossier 2 years later: what’s been corroborated and what's still unclear

July 2017: There was contact, but no 'collusion'

The Trump camp's explanation for its Russia contacts saw a significant shift in the summer of 2017, when a bombshell New York Times story revealed that three top campaign officials, including Manafort, son Donald Trump Jr., and senior adviser Jared Kushner met with two Russian lobbyists at Trump Tower.

After The Times reported on the meeting, Trump Jr. put out an initial statement claiming the meeting had nothing to do with Clinton or campaign business.

But the president's eldest son had to revise his statement several times after it emerged that he agreed to the meeting after he was offered "dirt" on Clinton. The offer, according to one email Trump Jr. received from the British music publicist Rob Goldstone, was "part of Russia and its government's support" for Trump's candidacy.

Then-President-elect Donald Trump speaks with his son Donald Trump Jr. during a news conference in the lobby of Trump Tower in Manhattan on January 11, 2017. REUTERS/Lucas Jackson

In response, Trump Jr. said, "I love it."

The full picture surrounding the meeting is still somewhat murky.

But it was reported last year that one of the Russian lobbyists, the Kremlin-connected lawyer Natalia Veselnitskaya, did not arrive with the promised dirt on Clinton, and instead wanted to discuss a potential repeal of the Magnitsky Act, which sanctions high-level Russians suspected of human-rights abuses.

Trump and his lawyers initially claimed that the president did not know about the meeting until The Times broke the story about it.

But the Washington Post later reported that Trump "dictated" the initially misleading statement his son put out after he was contacted about the story.

Trump later acknowledged that although the meeting took place in order to get compromising information on Clinton, it did not count as collusion because the campaign did not get anything from Veselnitskaya.

"This was a meeting to get information on an opponent, totally legal and done all the time in politics - and it went nowhere. I did not know about it!" Trump tweeted in August.

Read more:Mueller dropped an intriguing hint about where the Russia probe is headed in a new court filing

August 2018: Even if there was collusion, it doesn't matter because collusion isn't a crime

With Trump admitting he knew the meeting was to get damaging information on Clinton, his lawyers fell back on another strategy: arguing that collusion is not a crime.

"I have been sitting here looking in the federal code trying to find collusion as a crime," Rudy Giuliani, Trump's lead defense attorney, told Fox News in July. "Collusion is not a crime."

Trump echoed Giuliani in a series of tweets. "Where's the collusion? They made up a phony crime called Collusion, and when there was no Collusion they say there was Obstruction (of a phony crime that never existed)," he wrote.

"I don't even know if that's a crime — colluding with Russians. Hacking is the crime. The president didn't hack. He didn't pay for the hacking," Giuliani also told CNN.

Rudy Giuliani is Trump's lead attorney. Leah Millis/Reuters

Legal experts told Business Insider at the time that Giuliani's claim was a "red herring." While it is true that the word "collusion" is not a specific crime denoted in the federal code, they said that the focus is likely on whether the campaign was involved in a conspiracy to defraud the US.

"Mueller isn't investigating 'collusion.' He is investigating possible coordination between the campaign and the Russians, particularly any actual crimes committed in the context of that coordination," Bradley P. Moss, a lawyer specializing in national security issues, told Business Insider.

Read more: Here are all the ongoing investigations and lawsuits involving Trump and his businesses

"Russian companies and individuals have been charged with conspiracy to defraud the United States as a result of their alleged acts of election interference and hacking and distribution of emails," Harvard Law School professor and former federal prosecutor Alex Whiting said.

"If American citizens knowingly assisted these efforts, which could be described as 'collusion,' they could also be charged with conspiracy to defraud the United States," he added.

January 2019: There might have been collusion between Russia and the Trump campaign – but Trump himself wasn't involved

In a January 2019 appearance on "Cuomo Prime Time," Giuliani didn't rule out the possibility that members of the Trump campaign engaged in unlawful coordination with Russian entities and actors – but maintained that his client, Trump, was completely innocent.

"I never said there was no collusion between the campaign or between people in the campaign, I have no idea," Giuliani said. "I said there is not a single bit of evidence the President of the United States committed the only crime you could committed here: conspired with Russia to hack the DNC."

Giuliani's comments come after Paul Manafort's lawyers accidentally revealed in a recent court filing that Manafort shared Trump campaign polling data with Konstantin Kilimnik, a Ukrainian operative with ties to Russian intelligence.

Previous reporting has revealed that Manafort sought, at several points, to leverage his position as chairman of the Trump campaign to settle his debts with Russian oligarchs. He reportedly offered "private briefings" on the campaign to Oleg Deripaska, an oligarch to whom he owed around $30 million dollars, through Kilimnik.

Read more: Manafort's lawyers made a formatting error in a new court filing and accidentally revealed a slew of bombshells about his alleged lies to Mueller

After Trump's former personal lawyer Michael Cohen plead guilty to lying to Congress in 2017 testimony about the nature of the Trump Organization's attempts to build a Trump Tower in Moscow during the 2016 election, a sentencing memo from Mueller revealed more details about the Trump orbit's interactions with Russia.

The memo describes how "in or around November 2015, Cohen received the contact information for, and spoke with, a Russian national who claimed to be a "trusted person" in the Russian Federation who could offer the campaign "political synergy" and "synergy on a government level."

While this person is not named in the memo, BuzzFeed News reported in June that Cohen reached out to Russian weightlifter Dmitry Klokov about the project. Klokov claimed to be connected to Russian President Vladimir Putin. They were reportedly introduced by Ivanka Trump, then a vice president at the Trump Organization.