(CNN) US President Donald Trump's Russia problems seem to be getting worse by the week -- Attorney General Jeff Sessions has become the latest senior Trump official to be found within a murky web of ties and contacts to Russia.

But the communications between key Trump aides and Moscow officials are just some of the Russia-induced headaches for Trump that are threatening to overshadow his political agenda.

While some of Trump's Russia issues are mere nuisances, others could lead to more serious political -- and perhaps even legal -- consequences for the administration, experts say.

KEY PLAYERS

Here's what CNN has reported on the contacts and connections between former and current Trump aides and key figures in Russia and Ukraine.

CAMPAIGN CONTACTS WITH RUSSIA

Sessions told Congress during his confirmation hearing that he "did not have communications with the Russians," but now admits that he had two meetings with Russian Ambassador Sergey Kislyak. He insists the meetings were not to discuss the campaign.

The revelation was a blow for Trump, who just two weeks earlier encountered the exact same problem with his top security adviser, Michael Flynn , who resigned amid revelations he misled then-Vice President-elect Mike Pence about the nature of his own calls with Kislyak.

Just one day after Flynn stepped down, multiple officials told CNN that high-level advisers close to Trump were in constant communication with Russians known to US intelligence during the campaign period, naming then-campaign chairman and chief strategist Paul Manafort , who denied the accusations, and Flynn, who declined to comment.

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Another national security adviser to the Trump campaign, JD Gordon, has also disclosed that he had met with Kislyak , this time during the Republican National Convention in Cleveland in July. Gordon told CNN that he met Kislyak along with Carter Page and Walid Phares , who have also at points given policy advice to Trump.

In a statement to CNN , Page said he would not comment on any meetings and added that he "never did anything improper" with regards to Russia. Page did confirm that he met with Kislyak in Cleveland, however, in an MSNBC interview on Thursday.

Phares emphatically denied meeting with Kislyak in Cleveland. "I did not meet with the Russian ambassador, though I met with many other diplomats" in Cleveland, he wrote in a blog post for the New English Review on Saturday.

Trump's take: Russia ties are 'fake news'

Trump has branded the scandal over these ties as "fake news" and a narrative cooked up by the opposition Democrats to distract from their election loss.

Russia talk is FAKE NEWS put out by the Dems, and played up by the media, in order to mask the big election defeat and the illegal leaks! — Donald J. Trump (@realDonaldTrump) February 26, 2017

When asked about whether his campaign staff had been in contact with Russia, Trump replied: "Nobody that I know of. How many times do I have to answer this question? Russia is a ruse. I have nothing to do with Russia. Haven't made a phone call to Russia in years."

He defended Sessions Friday, calling him an "honest man" who "did not say anything wrong," adding that Sessions could simply have "stated his response more accurately."

Fallout: Trump's credibility takes a hit

Constitutional law experts say there will unlikely be legal ramifications over the Trump-Russia ties at this point. The fallout is far more likely to be political, and possibly within Trump's own Republican Party.

For now, it's Trump's credibility that has taken a hit, according to Larry Sabato, a political analyst from the University of Virginia who says that the Russian ties will have serious consequences for Trump's credibility.

"It's never a good thing for people to know that the Russians want you elected," he said.

He said Russia has been a major distraction to Trump's policy agenda, which is already challenging enough given Republicans are split over major issues, such as health care and tax reform.

In the fallout, Sessions has already recused himself from any investigation into Trump's election campaign.

As Attorney General, Sessions would have been the top authority over a probe into Russian activities in the US, as he has oversight of the Justice Department and FBI, which are carrying out one of several investigations into the matter.

Opposition Democrats called for him to step down from the investigation, but so too did some Republicans, showing a rift in Trump's party over the controversy.

Perhaps more significantly, if Sessions was found to have lied to or misled Congress, he could be accused of perjury. But even in that case, he is unlikely to be charged, according to Turley.

"The benchmark is quite high for perjury. They would have to show clear intent on part of Sessions to lie to the Senate committee both in his oral and later written responses," Turley said.

"His answer was, at best, inaccurate and inartful."

CRIMEA AND RUSSIA SANCTIONS

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Part of the controversy over Flynn's phone calls with Kislyak was that, according to a US official, he discussed sanctions with the diplomat before Trump took office.

The two men talked the day the Obama administration imposed fresh sanctions on Russia over its alleged hacking during the election, the US official told CNN. Flynn did not initially disclose this information to the FBI when asked about it.

The FBI is not expected to pursue any charges against Flynn, barring new information that changes what they know, law enforcement officials told CNN in February.

The Obama administration had previously sanctioned Russia over its annexation of Crimea from Ukraine in 2014.

Secretary of State Rex Tillerson -- who had close business dealings with Moscow in his previous role as CEO of ExxonMobil -- has been accused of opposing sanctions against Russia after its invasion of Ukraine. In 2013 he was awarded the Order of Friendship by President Vladimir Putin, one of the highest honors Russia gives to foreign citizens.

At his confirmation hearing in January, Tillerson claimed to the best of his knowledge that ExxonMobil had never lobbied against sanctions placed on Russia or Iran. But at a shareholders meeting in 2014, he did say that Exxon opposed sanctions in general, according to NBC

On Crimea, Ukrainian lawmaker Andrii Artemenko told CNN that he met with Trump's personal lawyer, Michael Cohen, to discuss a peace plan for Ukraine.

The exact details of the plan are unclear, yet reports have suggested it revolves around leasing Crimea -- annexed by Russia from Ukraine in 2014 -- to Moscow for 50 to 100 years. Artemenko declined to discuss the plan's details, yet hinted that a lease might be part of the idea.

Cohen offered to deliver the plan to the Trump administration, specifically to Flynn, Artemenko alleged.

Cohen admitted to the meeting, but denied delivering any documents to Flynn and that the Crimea plan was discussed, dismissing it as part of the "continued fake news narrative." The White House has flatly denied any knowledge of the proposal.

Trump's take: U-turn on Crimea

Trump in mid-January told the Wall Street Journal that he was open to lifting sanctions on Russia, though he planned to keep them for "at least a period of time."

Crimea was TAKEN by Russia during the Obama Administration. Was Obama too soft on Russia? — Donald J. Trump (@realDonaldTrump) February 15, 2017

Trump said he might scrap them if Russia helped the US battle against terrorists or with other goals important to the US.

"If you get along and if Russia is really helping us, why would anybody have sanctions if somebody's doing some really great things?" he said in the interview.

Trump's openness to working with Russia before he took office appeared to sour a month later when the President said emphatically on Twitter that Crimea was "taken" by Russia from Ukraine.

The comment was a glaring U-turn -- as a candidate, Trump had earlier hinted he might recognize Russia's annexation of Crimea in an interview with the ABC in August last year.

"I'm going to take a look at it," he said. "But you know, the people of Crimea, from what I've heard, would rather be with Russia than where they were."

Fallout: More pressure to get tough on Russia

As Obama had the power to impose US sanctions on Russia, Trump would have the power to lift them.

But as Russia is becoming something of an Achilles heel for Trump -- and as the Kremlin has upped its military posturing -- he has been under increasing pressure to harden his stance on Russia.

"It appeared at first he would likely lift [sanctions] on his own, but the politics around Russia have changed so quickly, he's far less likely to do so," said constitutional law expert Carlton FW Larson from the UC Davis School of Law in California.

"If the whole media narrative is you're a puppet of Vladimir Putin, you will do things to counter that idea."

This may explain Trump's Crimea tweet, but analyst Sabato says Trump's Twitter stance here is moot.

"Both Trump and Putin know that Trump isn't going to do a thing about Crimea -- and that's what matters. Putin doesn't care what Trump says on Twitter."

On allegations of Cohen's meeting with Artemenko, any suggestion that the White House might consider a plan such as the one allegedly presented to Cohen would likely cause consternation in Kiev and among its allies in Europe.

HACKING AND THE INVESTIGATION

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Some of Trump's Russia woes surround a US intelligence report, released in January, which found that Moscow ordered the hacking of Democratic National Congress email accounts in order to smear Hillary Clinton during the presidential campaign -- accusations that Russia has denied and called a "full-scale witch hunt."

The report concluded that Putin ordered an "influence campaign" to buoy Trump in the election, calling it "a significant escalation" in longtime efforts to undermine "the US-led liberal democratic order."

Trump's team was not implicated in the report, and there is no evidence connecting campaign aides to Russia-related hacking. But the probe was seen by Trump as an effort by US intelligence agencies to delegitimize his electoral victory.

The hacking investigation is separate to a larger investigation into Russia's activities in the United States. It is from this wider investigation that Sessions will have to recuse himself.

Trump's take: An evolution on who hacked DNC

Trump has flip-flopped on this issue, at first refusing to consider Russia may be behind the DNC hacks, also calling it a "political witch hunt."

He said on Twitter before his inauguration: "Only reason the hacking of the poorly defended DNC is discussed is that the loss by the Dems was so big that they are totally embarrassed!"

Only reason the hacking of the poorly defended DNC is discussed is that the loss by the Dems was so big that they are totally embarrassed! — Donald J. Trump (@realDonaldTrump) January 7, 2017

"I think it was Russia," Trump said. Putin "should not be doing it. He won't be doing it. Russia will have much greater respect for our country when I am leading it than when other people have led it."

Fallout: Sessions loses probe powers

The Sessions controversy -- along with Trump's loss of Flynn -- shows a president struggling to control his own team, analyst Sabato said.

But with Flynn gone and Sessions removed from oversight of Trump campaign-related probes, there is nothing that has emerged as yet that would warrant a legal response, Larson and Turley said.

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"The allegations that Russians intentionally hacked emails is certainly serious but it's not unprecedented. The US has also been long accused of attempting to influence foreign elections, and those attempts go back to the 1700s. That alone doesn't create a criminal act," Turley said.

"I also don't think most citizens believe that those hacked emails made a material difference to the election results. When Clinton was nominated, she was already the most unpopular candidate. She had more baggage than a Greyhound."

But the investigation is in its early days.

"A real fallout would come if, for example, Trump is found to have clearly lied about having no investments in Russia ... or if some major moguls and billionaires there were conspiring to help Trump win. That would have an impact," Sabato said.