What is going on between Mr Vladimir Putin and Mr Donald Trump? That question hung over the United States election. Now that Mr Trump has won the presidency, the question of his relationship with the Russian leader assumes global significance.
Mr Trump's statements are often confusing and contradictory. But on Russia, he has been pretty consistent and clear. He regards Mr Putin as a strong leader, worthy of admiration, and wants to see a sharp improvement in US-Russian relations. As Mr Trump put it recently: "Wouldn't it be great if we actually got along with Russia?"
Mr Trump's America will clearly try to strike a deal with Mr Putin's Russia. But what would that deal look like? Here is my best guess.
The US will end its opposition to Russia's annexation of Crimea. Although America may not agree to the formal legal incorporation of Crimea into Russia, it would accept it as a fait accompli. Following that, the US will lift economic sanctions. The Americans will also drop any suggestion that Ukraine or Georgia will join Nato. The build-up of Nato troops in the Baltic states will also be slowed or stopped.
In return for these large concessions, Russia will be expected to wind down its aggression in eastern Ukraine and not attempt to make further territorial gains there. Russian pressure and implicit threats towards the Baltic states of Estonia, Latvia and Lithuania will be dropped. Military tensions on the front line between Nato and Russia will be dialled down. With their conflict in eastern Europe eased, the US and Russia will make common cause in the Middle East. The US will drop its commitment to the overthrow of President Bashar al-Assad in Syria and will join the Russians in an attack on the ISIS militant group.
The attractions of such a deal from Mr Trump's point of view are obvious. If it worked, it would defuse an increasingly dangerous confrontation between the US and Russia. During his campaign, Mr Trump accused Mrs Hillary Clinton of risking a third world war: a reference to her promise to declare a "no-fly zone" over Syria, which might have led to confrontation between the US and Russian air forces. Abandoning the Obama administration's goal of getting rid of Mr Assad would also resolve the longstanding incoherence in the US' Syria policy, which sometimes seemed to place America on both sides of a civil war.
Reducing tensions in eastern Europe would also be a considerable prize, given that Russia has just moved nuclear weapons into Kaliningrad, which lies between Poland and Lithuania. Finally, the lifting of sanctions and the return to commerce as usual would appeal to the businessman in Mr Trump.
Yet while the attractions of such a deal are clear, the potential pitfalls are huge. First, allying with the butchers of Aleppo would involve a level of calculating amorality that will revolt many in America and Europe.
Second, it involves placing a huge amount of trust in Mr Putin's willingness to keep his side of the bargain - rather than simply pocketing concessions and then coming back for more, perhaps in the Baltic states. Mr Newt Gingrich, former speaker of the US House of Representatives and now likely to get a top job under Mr Trump, recently said Estonia is in the "suburbs of St Petersburg" - which hardly suggests an unequivocal commitment to the independence of that country.
The amorality of making common cause with Mr Assad and Mr Putin is unlikely to trouble Mr Trump. Asked early in the campaign about Mr Putin's alleged habit of killing journalists, Mr Trump replied: "Our country does plenty of killing too." Mr Trump has also endorsed torture, so he is unlikely to be squeamish about a de facto alliance with the Assad regime.
Even so, it would be a huge gamble for the US President-elect to place his faith in his wily, experienced Russian counterpart. If Mr Putin were to renege on his promises, Mr Trump would look like a chump, and he hates that.
In the end, a lot may depend on how Mr Trump and his advisers assess Russian motives. Most of the foreign policy establishment in Washington will warn Mr Trump to be deeply suspicious of Mr Putin and will argue that any American concessions will be seen as weakness and encourage further Russian aggression.
But a rival school of thought argues that what Mr Putin wants, above all, is respect. This school believes that if Washington treats Moscow as an equal, and makes it clear that America has no intention of encouraging Russia's liberal opposition, then a "new deal" with Russia is possible.
A deal constructed along these lines would essentially represent a return to a Nixonian approach to Moscow, with the White House attempting a new form of detente with the Kremlin. It is even possible that 93-year-old Henry Kissinger, who served as Mr Richard Nixon's secretary of state, could play a role as an adviser or intermediary. Dr Kissinger still travels widely and has been invited to Moscow this month.
In the 1970s, however, Dr Kissinger was dealing with an increasingly sclerotic Soviet Union led by the relatively cautious Leonid Brezhnev. Attempting a new detente with the aggressive and risk-taking Mr Putin is a different and much riskier proposition.