The fear is dangerous needling of already-fraught U.S. social turmoil.

The big picture: Espionage and trickery between the West and Russia is not new — it goes back to Peter the Great, 3 centuries ago. But scholars say they are pressed to identify any episode of direct political mischief-making in this long history comparable to the breadth, scale and intensity of the Russian hacking, leaking and social media campaign in the 2016 U.S. election.

When it comes to its rivals and enemies, Moscow's objective often is to create chaos, and thus incapacitate the other power as a threat to Russian aims.

and enemies, Moscow's objective often is to create chaos, and thus incapacitate the other power as a threat to Russian aims. To get there, the weapon of choice is usually the exploitation of existing divisions in the other society.

the weapon of choice is usually the exploitation of existing divisions in the other society. That is where, in 2016, the U.S. made itself a sitting duck — and where polarized, ultra-bellicose Americans remain perhaps even more exposed to emotional manipulation in the coming election.

Russia hands in Washington and elsewhere are worried. No one can say with absolute certainty that Putin will attack this time, nor if he does, what means he will use. But what no one disputes is that the country — despite mountains of descriptions of Russia's actions last time — is little-better prepared now to defend itself than it was 3 years ago.

In 2016, the GRU — Russia's military intelligence arm — carried out the hacking of Clinton adviser John Podesta's emails and documents at the Democratic National Committee, according to the investigative report by special counsel Robert Mueller. At the same time, the Kremlin-backed Internet Research Agency was behind the massive social media campaign to provoke discord.

President Trump and Republican leaders at the federal and state levels have stifled efforts to form a national political strategy to combat a redux of the Russian campaign. One reason: Trump seems to view such efforts as challenges to the legitimacy of his 2016 victory.

have stifled efforts to form a national political strategy to combat a redux of the Russian campaign. One reason: Trump seems to view such efforts as challenges to the legitimacy of his 2016 victory. While the defenses remain down, Trump appears especially prepared to stoke rawpolitical, societal and social emotions, often amplified by political commentators and talk show hosts at Fox and other media outlets.

Trump appears especially prepared to stoke rawpolitical, societal and social emotions, often amplified by political commentators and talk show hosts at Fox and other media outlets. "If Putin is going to throw the match of chaos, he needs kindling here. Our political system provides far too much of it right now," says Richard Fontaine, CEO at the Center for a New American Security.

Some possibilities of what's next:

Aric Toler, lead researcher at Bellingcat, a European investigative organization, says that if he had to choose one possible Putin plan for the U.S., it would be more of the same — "a lot of ad hoc actors within and from outside the Russian government/security services with similar targets as in 2016."

a European investigative organization, says that if he had to choose one possible Putin plan for the U.S., it would be more of the same — "a lot of ad hoc actors within and from outside the Russian government/security services with similar targets as in 2016." Mark Galeotti, a leading scholar on Russian intelligence and author of "We need to talk about Putin," foresees an effort "to escalate and magnify the inevitable divisions that become exacerbated in election times. With Trump running, and many Democrat voices prone to castigate his supporters as racists and morons, these opportunities are likely to be plentiful."

The bottom line: "I see no reason to expect that U.S./Western actions since 2016 have changed Moscow’s appetite for risk. Buckle up," said Andrew Weiss, a Russia expert at the Carnegie Endowment.

A wild card: A Russia expert contact of mine formerly with Britain's MI-6 said that, if Putin's strategy is what's expected — to do whatever will best polarize the U.S. — he may choose to do nothing. "Trump seems to be doing a pretty good job all by himself, depending on where you sit, so it might be easier to leave well alone."