The unprecedented claims injected an explosive new element into the unpredictable 2016 campaign, after emails purportedly from a Russian hack and published by WikiLeaks appeared to show collusion among top Democratic officials -- who are supposed to stay neutral -- against Hillary Clinton rival Bernie Sanders.
But the spying drama also poses much deeper questions about Moscow's stance towards the next president -- whoever it is -- and the escalating East-West confrontation between major powers whose leaders are more estranged than at any point since the Cold War and still maintain competing nuclear arsenals.
Putin's grudge against the West
Disclosures that cause discord in the U.S. and sully American democracy can only benefit Putin's core political project -- chipping away the West's political institutions to weaken the power of what has been called the free world.
And the Russian leader clearly nurtures deep personal animosity against the Obama administration and Clinton, its former secretary of state.
It's beyond question that the former KGB agent in the Kremlin has the means, through Russia's sophisticated intelligence services, to sow mischief in the U.S. presidential election. And Putin has the motivation -- a long-simmering grudge against the West.
"Was the 2016 election a target?" Matthew Rojansky, director of the Kennan Institute at the Wilson Center, said of Russian intelligence agencies. "The answer is very plausibly yes."
A harder case to prove is Democratic accusations that Russia carried out the DNC hack in order to advance the candidacy of Republican nominee Donald Trump.
"What the experts said when this breach initially happened at the DNC was that they believed it was Russian state actors who took these emails," Clinton campaign manager Robby Mook said on Monday.
"What further experts are saying is that then, because they possessed those emails, that Russian state actors were feeding the email to hackers for the purpose of helping Donald Trump," he claimed.
While forensic evidence will likely prove conclusively whether the hack originated in Russia, it may be impossible to clearly establish Putin's own complicity in the operation, or the motivations of the Russian government.
The FBI confirmed Monday that it was investigating a hack into the DNC. U.S. officials suspect the intrusion was a Russian cyber hack, though the State Department said it was important for the investigation to run its course before making any determinations. But private-sector cyber security investigators hired by the DNC concluded that hackers working for the Russian government were behind the year-long breach of the committee.
Putin the super PAC?
But Putin's behavior since returning to power in the Kremlin -- after being the silent hand behind former president Dmitry Medvedev for the preceding four years -- lend credence to the idea that Russia is attempting to play politics in the U.S.
The Russian president has made no secret of his desire to weaken the West, his belief that the U.S. and its European allies have conspired against Russian interests in Georgia, Ukraine, Libya and Syria, and sees a restoration of Russian global prestige at the expense of the West as paramount.
Undercutting America's political system and thereby impeaching its ability to judge others would further that goal in Russian eyes.
"It is very consistent with a Russian approach," said Fiona Hill of the Brookings Institution, who co-authored the book "Mr. Putin: Operative in the Kremlin."
"The whole purpose of Russian propaganda is to show that the U.S. and U.S. politics is filled with hubris and hypocrisy and to show it is not better than anyone else," Hill said. "Putin operates like a super PAC, taking advantage of opportunities for negative campaigning. The purpose is to show that the U.S. has no moral authority."
Putin's beef with Clinton
Putin also has a personal reason that he could want to intervene in America's democracy: He's convinced the U.S. orchestrated its own covert campaign against him that threatened his rule, and he has a personal grudge against Clinton as well.
Putin, while serving as prime minister, forcibly denounced the then-U.S. secretary of state in 2011, saying she had condemned Russia's parliamentary elections as fraudulent before she had evidence and directly incited anti-government protests.
The U.S. government dismissed the claims as absurd at the time.
But people who have studied Putin closely suggest that the episode further cemented the Russian leader's conspiratorial mindset and a worldview framed by his experience as a KGB officer when the Soviet Union crumbled.
"In 2011 and 2012, Putin literally thought that the U.S. was orchestrating a color revolution in the streets against him," said Rojansky. "He thought there was an intelligence operation against him. He could smell it."
Washington has rejected such claims, but the reality looks different from the Kremlin's point of view.
Former ambassador: I'm appalled
President Barack Obama's one-time ambassador to Moscow, Michael McFaul, was a renowned expert on the democratization of Eastern Europe. He also conducted meetings with Russian opposition figures -- standard practice for a U.S. diplomat overseas but one that sparked suspicion in Moscow.
McFaul, who endured a campaign of intimidation by Russian security services while in Moscow, added credence Sunday to the idea that Russian was behind the DNC hack.
"As U.S. voter, I'm appalled by Russian meddling, want it investigated & stopped. As long-time analyst of Russia, Im (sic) impressed; they're good," McFaul tweeted.
McFaul was also an architect of the "reset" of relations with Russia early in the Obama administration when he was a National Security Council official. It prioritized relations with new Russian President Dmitry Medvedev. Some analysts believe that bypassing Putin at the time may have deepened his paranoia about U.S. intentions.
And Putin was infuriated by what he saw as the West pulling the wool over his eyes during a U.S.-led mission in Libya. The operation to avert genocide there was governed by a U.N. Security Council resolution that Russia allowed to pass only to see the effort go on to topple Moammar Gadhafi.
The Russian leader also saw American calls for the ouster of Syria's President Bashar al-Assad -- a close Russian ally -- as a bid to weaken Moscow's influence in the Middle East. And analysts have said that he believes that the 2014 revolution in Ukraine that ousted a pro-Russian ruler was instigated by the U.S.
Trump: The new Berlusconi?
At the same time, Putin might see a friendlier face in Donald Trump. The billionaire businessman has publicly spoken warmly about Putin and sent alarm surging through Europe by repeatedly casting doubt on NATO's mission and U.S. security guarantees to member states threatened by Russia.
"Hillary and (German Chancellor Angela) Merkel represent an existential threat to Putin's regime," said Arkady Ostrovsky, who wrote about the Russian leader's rule in the new book "The Invention of Russia."
"Trump doesn't represent an existential threat to Putin's regime. He represents a threat to stability in the world, but given that Putin loves exploiting chaotic situations, I think he feels he would only win with Trump," Ostrovsky said.
Furthermore, some analysts say Putin sees Trump as akin to former Italian Prime Minister Silvio Berlusconi, who like the U.S. billionaire lacked depth in global affairs but was a master media manipulator and got on with the Russian leader well.
And as a world leader addicted to deal making, Putin apparently believes he could outsmart Trump at the negotiating table.
Could the DNC hack backfire?
But claims that Putin is deliberately intervening to tilt the electoral battleground will be more difficult to prove and strike some analysts as a stretch.
Even if the hack at the DNC fits in with wider Russian security policy that has used the media, covert cyber operations and support for anti-establishment groups in Europe as tools in information warfare, it is unclear whether Putin -- even if he favors Trump -- would sanction an effort to try to elect him.
"I think we have to ask, who does this help?" Russia analyst Jill Dougherty told CNN International's Hala Gorani in an interview. "Having the implication that you are being helped by Vladimir Putin may not be a very good thing in this context and so it could backfire."
The Trump campaign is aware of the risks. It has vehemently denied any suggestion that its candidate's fortunes are helped by Russian intervention and blasted the suggestion as dirty politics by the Clinton campaign.
The Trump camp was also thrown on the defensive by reports about campaign chairman Paul Manafort's own past ties with pro-Moscow politicians in Ukraine.
How deeply the Russia issue will shape the campaign remains unclear. It could resonate badly for Trump in swing states in the Midwest with high concentrations of Latvian, Lithuanian, Polish, Ukrainian and other ethnic Eastern European voters.
But Russia could end up winning either way. If Trump and his skepticism toward NATO doesn't take the White House, a weakened Clinton at the head of a frayed Democratic Party and a damaged democratic system also serves Moscow's purposes.
"(Putin) can't influence the course of the election but what he can do is show whoever is elected is no better than their opponent," said Hill. "It's kind of a win-win."