As special counsel Robert Mueller's investigation into possible Russian meddling in the 2016 US election heats up, President Donald Trump's former personal lawyer Michael Cohen was revealed to be cooperating with the investigation following his guilty plea on Thursday for lying to Congress.

One of Donald Trump's longest-serving former aides, former White House legislative director Marc Short, downplayed the importance of Cohen's guilty plea.

"What you have seen in the last 24 hours is that the president's opponents are trying to pitch it as a bigger deal and his defenders are saying the real estate deal went nowhere and so it is not really a conflict," Short told DW. "I think it's more of the same, honestly."

Asked how he personally viewed the Cohen plea, Short, who served the Trump campaign as an adviser to Trump's running mate and current Vice President Mike Pence, said he did not think there was any collusion between the Trump team and Russia.

"Having served in the campaign, but I mostly was traveling the country with the vice president because I was on his team, I never saw any evidence or have any belief that there is any collusion with Russia," said Short. "I am not real worried about that."

Watergate prosecutor: 'Major indictment' coming

Some legal scholars, however, have argued that Cohen's guilty plea is in fact very significant because it could lay the groundwork for possible future prosecutions or indictments against people in the president's orbit.

"What it means is that Mueller is teeing up a major indictment against other individuals relating to the conspiracy between Russia and the Trump campaign," said Nick Akerman, an assistant special Watergate prosecutor.

The only reason to have Cohen, who already pleaded guilty to previous charges, testify to additional crimes is to prepare him as a future witness in upcoming indictments on similar issues, said Akerman.

"As a prosecutor what you really want to do is ... have your accomplice witness plea to something that is akin to what he is going to be testifying about against others," Akerman said. "What Mueller was really doing here was setting up Cohen to be a witness in a trial of others in the US that were involved in the conspiracy with the Russian government."

Read more: Trump's ex-campaign boss Manafort 'lied' to FBI

Cohen plea 'establishes a corrupt motive' for Trump

Jens David Ohlin, a law professor and vice dean at Cornell University, concurred that the Cohen plea could be used as a stepping stone to additional indictments. But he noted that even on its own, the guilty plea by Trump's former personal lawyer and fixer is relevant.

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"The significance is that it establishes a motive for Trump to be so solicitous of the Russians — and it establishes a corrupt motive," said Ohlin.

It was already widely assumed that Trump may have had a financial incentive to be beholden to Russian government officials because he wanted them to help him secure a business deal to build a Trump Tower in Moscow. Cohen's plea now appears to confirm that assessment, the professor added.

What's more, Cohen's plea strengthens the argument that there was repeated contact between the Trump campaign and Russia. Notably: Trump's former National Security Adviser Michael Flynn pleaded guilty to lying to the FBI about his contacts with Sergey Kislyak, the Russian ambassador in Washington; the Trump Tower meeting in New York at which top campaign officials, including Trump's son Donald Jr. and his son-in-law, Jared Kushner, met with a Kremlin-connected Russian lawyer reportedly hoping to acquire damaging information about Democratic presidential candidate Hillary Clinton; the reported connections between Republican strategist Roger Stone and WikiLeaks; and now Cohen's plea about more extensive and longer contacts with Russian officials regarding real estate in Moscow.

"Those are four different avenues where there were contacts with Russia, so it is just not a situation where it is believable to say there was absolutely no contact with Russia," said Ohlin. "Any one of those alone might be problematic."

Trump could be an 'unindicted co-conspirator'

"Where we go from here is a number of people go to jail," predicted Watergate prosecutor Akerman. He said he expects "a blockbuster indictment" of various people in Trump's orbit and argued that anyone present or involved in the Trump Tower meeting could be indicted by Mueller, including Donald Jr. and Kushner.

Trump himself may not be indicted by Mueller since the special counsel might adhere to the Justice Department's policy of not indicting sitting presidents, added Akerman. But, he said, Trump could be named an unindicted co-conspirator as happened with former President Richard Nixon.

"It all just comes together; the puzzle pieces are falling into place," Akerman said.

Cornell legal expert Ohlin added, "I would say the outer boundaries of the picture are complete and what Mueller has to do now is sharpen the resolution of the picture by adding more details."

Trump's son-in-law and close adviser Jared Kushner (pictured) may be facing indictment, along with Trump's son Don Jr.

Ex-White House aide: Lying should be prosecuted

Short, Trump's former legislative director, offered cautious criticism of the Mueller probe, which he said he views as straying from its intended course.

"I think in this case, this is supposed to be an investigation about Russian interference in the election and it seems that right now where the prosecution is gone is Manafort's not registering as a foreign lobbyist — was he honest or dishonest in his filing — and similar with Cohen's statements," Short said. "It's not to condone any activity that is illegal and, certainly, lying — those should be prosecuted to the fullest extent of the law, but that is not what the focus of the investigation was supposed to be."

Mueller was, however, granted power to investigate additional crimes uncovered during his investigation.

Trump and his lawyers 'acting worried'

Asked about Trump's behavior in the wake of Cohen's plea, Ohlin said: "I think he is worried, I think he is acting worried, and I think his lawyers are acting worried."

While Trump's legal team had been successful in the past half year in preventing the president from acting rashly and making things worse for himself, Ohlin predicted that might be more difficult if things come to a head and close associates or family members get indicted.

"There is absolutely no constitutional barrier to Mueller indicting a member of Trump's family for lying to the FBI, lying to Congress or obstruction of justice or anything like that," Ohlin said. "An indictment like that puts Trump in the weakest possible situation and may force him into acting very rashly and that could be his own undoing."

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