Many unorthodox things have taken place in the 2016 race for the White House, but Russia is perhaps the most unlikely guest at the US political dinner table.
From US accusations that Moscow hacked emails of Democratic Party leaders to hurt Hillary Clinton, to her charge that opponent Donald Trump is a "puppet" of Russia`s Vladimir Putin, one might be forgiven for thinking it`s 1960, not 2016.
The outsized spot for Russia in the campaign is unusual and, experts say, shows how difficult ties are between the former Cold War rivals, especially over Syria, Ukraine and cyber threats -- and how far apart the contenders are on how to fix them.
"In past elections, candidates` positions on Russia were much closer," explains Timothy Frye, chair of the political science department at Columbia University in New York.
"In this election, Trump has taken a position directly at odds with that of Clinton and at odds with the foreign policy establishment. Mr Trump`s position is extreme even by the standard hawk-dove criterion."Moscow`s arrival on the US election scene first drew attention in late 2015, when relations were already fraught following Russia`s annexation of Crimea from Ukraine and the launch of its bombing campaign in Syria.
At that time, Putin described the Republican Trump as a "very bright, talented person." 
The real estate billionaire returned the compliment, praising the Russian leader as a strong leader, "unlike what we have in this country."
Russia`s involvement has grown since then, with what experts believe to be a major hacking campaign that included the leaking of more than 20,000 emails from Democratic Party leaders, as well as alleged Russian links to Trump`s former campaign manager Paul Manafort.
In her second debate with Trump earlier this month, Clinton lashed out at Moscow.
"We have never in the history of our country been in a situation where an adversary, a foreign power, is working so hard to influence the outcome of the election," she charged.
Russia has flatly denied the hacking accusations, with Foreign Minister Sergei Lavrov dismissing them as "flattering" but "ridiculous." 
Moscow "was, is and will be committed to the principle of the need to fight cyberterrorism and hacking," Kremlin spokesman Dmitry Peskov added.
Then during the final presidential debate last week, Trump boasted that only he could improve relations with Moscow because Putin has "no respect" for Clinton.
"That`s because he would rather have a puppet as president of the United States," the Democrat shot back during a fiery exchange.
"No puppet. You`re the puppet," he retorted.Such attention to Moscow in an American presidential campaign is "unprecedented," said Frye. 
"It is a direct reflection on the state of the relationship, which is at its lowest since the Cold War," he told AFP.
For Frye, Clinton may have a pointed interest in pushing the subject of Russia.
"Hillary sees that as a winning issue, especially among voters of Eastern European descent," he said.
"Swing states like Pennsylvania, Ohio, Michigan all have sizeable Ukrainian, Polish and other Eastern European population for whom Russia is a particularly strong issue."While Russia has insisted it had no role in Democratic party email hacks, its hostility towards Clinton is in no doubt.
The Kremlin`s massive state media machine has covered every scrap of controversy surrounding the former secretary of state -- and highlighted every Trump statement deemed favorable for Russia.
Observers trace the Kremlin`s animosity for Clinton back to Russia`s parliamentary elections in December 2011, when several mass protests presented Putin with his biggest-ever challenge as Russian leader.
Tens of thousands took to the streets to denounce vote fraud. 
Two days after the elections and before the protests began, Clinton -- then at the State Department -- called for a full investigation into the accusations, citing "serious concerns about the conduct of the election."
Her criticism deeply riled Putin, who accused her of meddling in Russia`s affairs and saying she had given opposition activists some kind of "signal" to act.
In that context, Trump`s recent warnings about the "rigging" of the US election "are music to the ears of those who have a very cynical view of the United States -- in Russia and elsewhere," Frye said.
But as a Clinton victory looks more and more likely, the Kremlin will need to find a way to work with her, according to Stephen Sestanovich of the Council on Foreign Relations in New York.
"The question is not whether they will be prepared to talk, but what they will talk about," he said.
"Unlike the situation in the past 25 years, when there would be one disagreement at a time, now it`s a really full plate of disagreements."