(CNN) Rarely has a presidential summit between the United States and Russia been so badly needed yet so spectacularly undermined by timing and circumstance.

But there has also never been a chapter in the long history of superpower showdowns and historic Cold War-ending negotiations to match the surreal nature of Monday's encounter between US President Donald Trump and Russian President Vladimir Putin

There are multiple reasons why it's good for the two Presidents to talk given critical national security issues including the war in Syria North Korea , fraying arms control agreements and the desperate state of relations between two nuclear powers with the capacity to wipe out humanity.

If they make progress against expectations, then the President's critics may have to eat their words. Even if the talks unfreeze lower level dialogue, they may be worthwhile.

Yet worthy diplomatic openings will pale against the mind-boggling spectacle of the most unusual US-Russia summit in history.

After all, Trump will sit down with the man accused of masterminding an audacious election meddling operation in order to put him into office, days after the indictment of Russian intelligence operatives by his own Justice Department, in the Robert Mueller-led probe the US President has branded a "witch hunt."

It's not even clear that Trump will upbraid Putin over such a brazen assault on American sovereignty and democracy -- despite being given considerable leverage by the staggering indictments.

On the eve of the talks, Trump offered little sign he is lining up big outcomes.

"I go in with very low expectations. I think that getting along with Russia is a good thing, but it's possible that we won't," Trump told CBS News in an interview broadcast Sunday

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It's not surprising therefore that Democrats and some Republicans question why the summit is still on, especially given the administration's failure to provide a clear sense of the agenda and possible deliverables of a confab Trump has craved for months.

There are fears in Washington that the winging-it US President will cough up big concessions in a comprehensive mismatch with the wily and prepared Russian veteran.

Trump's insistence on a one-on-one meeting with Putin without senior aides present has refocused intrigue on his odd relationship with a strongman he never criticizes and fueled speculation he is somehow beholden to the former KGB agent and intelligence chief.

It's also curious that Trump often appears more in tune with Putin's views than those of his own government on Crimea, the unity of the Western alliance, the special counsel probe and democratic bedrocks like press freedom and international institutions.

Given the inauspicious atmosphere, it's unlikely that any other President would still be meeting Putin. Trump's decision to press ahead anyway has left US officials floundering.

Before Trump left for Europe, US Ambassador to Russia Jon Huntsman said: "I think the fact that we're having a summit at this level, at this time in history, is a deliverable in itself."

But on Sunday he undercut his own expectations-building.

"It isn't a summit. I've heard it called a summit. This is a meeting," Huntsman said on NBC's "Meet the Press," styling the sit-down as an initial chance to defuse boiling tensions.

Presidents who can't wait to meet

There is no doubt the summit is going ahead simply because Trump and Putin want it to.

Trump relishes the pageantry of international set pieces in which he bestrides the world. He also seems most at home with strongmen like Putin, North Korea's Kim Jong Un or China's Xi Jinping, unencumbered by international institutions, allies or America's traditional foreign policy.

Putin enters the summit on a roll, after presiding over a successful World Cup final in Russia. He can use it to build legitimacy for his autocratic rule at home, by showing that he has restored Russia to great power status after the humiliation of the Soviet collapse.

As a bonus, he got to watch this week as the President in the United States enacted the core goal of his own foreign policy, carving deep divisions between the US and its NATO allies, insulting America's friends such as German Chancellor Angela Merkel and British Prime Minister Theresa May and deepening polarization in American politics with assaults on the Russia probe.

And he gets to greet the President in private. The rest of the world may never know the content of the encounter, given their propensity of both men to shade the truth.

Trump's rationale for the talks -- as he has repeatedly stressed on his trip to Europe -- is that it would be better for the world if the US and Russia got along.

"In a sense, we're competitors ... he's not my enemy. And hopefully, somebody, maybe he'll be a friend," the President said in Brussels last week.

In Montana this month, Trump scoffed at the idea Putin was an enemy dedicated to zero-sum combat with the United States.

"You know what? Putin's fine. He's fine. We're all fine. We're people," he said.

Trump's attitude marks a sharp shift from the attitude of his two predecessors. Former presidents George W. Bush and Barack Obama both made clear privately that although they had hoped to forge cooperation with Putin, they came to see him as motivated by deep resentment and even paranoia about the United States, brewed by fury over what he saw as disrespect meted out to Russia in the post-Cold War era.

Perhaps, therefore, treating Putin as an equal of the American president could indeed work and validate Trump's approach.

But many experts believe that he is underestimating the Russian leader, especially after he said before leaving the US that the Putin meeting would be the "easier" leg of his trip.

For Putin, read Kim

Trump critics worry that Putin will have evaluated Trump's summit with Kim in Singapore as he seeks to outmaneuver the President in Helsinki.

They note that Trump offered up a significant concession to Kim -- a halt to US military exercises with South Korea, without getting much in return, let alone a verifiable pledge to dismantle Pyongyang's nuclear program

"Trump gave up lots of things and got absolutely nothing from the North Koreans except for one thing, which was the one thing he wanted -- enormous flattery," said Kenneth Adelman, a former senior arms negotiator at US-Soviet summits with President Ronald Reagan.

"I think Putin will be wonderful at this to say 'Oh My God, we had such great rapport, we just get along so well,' -- that is all that Trump really wants," Adelman told CNN's Don Lemon Friday.

There is anxiety in Washington that Putin could convince Trump to hand over areas of Syria to Russia's client Bashar al-Assad, in a way that will benefit Iran, because of his eagerness to get US troops home.

In Europe, allies worry that Trump could agree to downgrade alliance military maneuvers, even though he endorsed an alliance communique highlighting malign Russian influence and has drummed up extra defense spending by foot-dragging member states.

And after Trump raised the possibility of recognizing Putin's annexation of Crimea, there will be intense scrutiny of his rhetoric on the issue at a joint news conference.

The top talking point may be how Putin and Trump navigate the election interference storm.

Trump pledged Friday to raise the issue, but has repeatedly said he knows Putin will deny involvement.

While the indictments handed down by special counsel Robert Mueller on Friday increase political pressure on Trump, they did not change his attitude towards the investigation.

He is now blaming the special counsel for the tortured state of relations with Russia.

"I think we're greatly hampered by this whole witch hunt that's going on in the United States, the Russia witch hunt, the rigged situation," Trump told CBS.

Putin knows the President is under intense pressure and has little interest in seeing him further damaged -- so it's not impossible he could offer a public acknowledgment that some Russian hackers may have transgressed or style the election meddling as everyday espionage.

Russian officials also often paraphrase the President's own rhetoric in an apparent effort to offer Trump validation for his complaints that he rarely gets from US critics.

Trump's sometime ally, Republican Sen. Rand Paul of Kentucky, questioned whether demands for a Russian confession were worthwhile.

"I think, really, we mistake our response if we think it's about accountability from the Russians. They are another country. They are going to spy on us. They do spy on us," Paul said Sunday on CNN's "State of the Union."

But Democratic Congressman Adam Schiff said Putin was essentially an "unindicted co-conspirator" in the Russia probe.

"He's the ringmaster of this conspiracy and he's going to be sitting down at the table with Donald Trump and Trump is basically saying that indictment is just a witch hunt," he said, also on CNN's "State of the Union." "That's a great gift for Vladimir Putin."