Did President Putin just blink? And if he did, what did he mean by it?
He's good at being hard to read, is Mr Putin. And I suspect he rather enjoys it. So in Western capitals this weekend, after a bigger-than-usual Victory Day parade in Moscow, the question is simply this: has Russia stepped back from the brink in Ukraine?
The Russian president said two significant things this week - first, that he wanted pro-Russian activists in eastern Ukraine to call off their separatist referendum planned for this weekend; and second, that Ukraine's presidential elections, scheduled for later this month, could be a move "in the right direction". That's not what Moscow was saying just a few days ago.
As things stand, the pro-separatists insist that they will go ahead with the referendum, with or without Mr Putin's blessing. But at least now he can claim that he did what he could to halt it - and hope, in so doing, to lift the threat of further sanctions being imposed.
So - perhaps - the most serious crisis in East-West relations since the end of the Cold War may be about to ease. We'd be wise, though, not to start celebrating just yet. What Mr Putin says, and what Mr Putin does, are not always in perfect harmony.
But let's just suppose that he is indeed trying to lower the temperature a few degrees. And let's consider what could have led to an apparent change of heart. I have never believed that he was planning a full-scale military takeover of eastern Ukraine, but it did look as if he was, at the very least, encouraging pro-Russian fighters to usurp the authority of the interim government in Kiev.
One possibility is that Moscow has come to fear the consequences of a full-scale civil war on Russia's doorstep. Mr Putin can't have relished the prospect of thousands of refugees trying to cross the borders to escape the violence, nor the threat of unrest spreading into Russia itself.
A second possibility is that the impact of the sanctions already imposed by the US and EU has been greater than he expected. The Russian economy was in pretty poor shape even before the Ukraine crisis exploded -- and according to Mario Draghi of the European Central Bank, a staggering $220 billion may have left Russia over just the past few weeks.
But there's a third possibility that I find even more intriguing. Because according to a fascinating new survey of public opinion in Ukraine, Russia is a lot less popular, even in the supposedly pro-Russian east of the country, than you may have been led to believe.
The poll was carried out last month by the highly-respected Washington-based Pew Research Centre, and in its report published yesterday it says that 70 per cent of people in eastern Ukraine want the country to remain united. Even among people who identify themselves as Russian-speakers, barely a quarter are in favour of their region seceding.
I don't suppose Mr Putin got advance notice of the poll's findings. But perhaps some brave Kremlin official did venture to suggest that the sight of Russian troops massing on Ukraine's borders - to say nothing of those mysterious "little green men" who have been popping up wherever there's trouble (most Ukrainians seem to be convinced that they're Russian military personnel) - is not going down too well.
According to the Pew survey, far more Ukrainians are suspicious of Russia (67 per cent) than they are of the EU (33 per cent) or the US (38 per cent). Even among Russian speakers in the east of the country, fewer than half expressed confidence in President Putin.
Foreign leaders who see themselves as liberators (hello, Mr Bush and Mr Blair?) are often surprised when their self-image isn't shared by the people they thought they were liberating. So maybe Mr Putin is having second thoughts: does he really want to take on responsibility for a slice of a neighbour's territory where most of the people don't seem too keen on him?
In Crimea, by the way, it's an entirely different picture: the Pew survey suggests that more than 90 per cent of people in Crimea think well of the Russian president and say that their pro-secession referendum in March was conducted freely and fairly.
And of course, there's always the bigger picture as well. Mr Putin has long been suspicious of what he regards as US manoeuvring along Russia's borders: according to the former Kremlin adviser Alexander Nekrassov, he believes the Ukraine crisis stems from "a US desire to redraw the economic map of Europe, to start sorting out its enormous debts that are spiralling out of control."
The Moscow view is that the US is constantly looking for new markets, including in Europe, and that the US endgame is to run Europe while freezing out Russia. Back in February, I wrote: "Putin understands the nature of power, and he knows better than any other current world leader how to use it." For now at least, I stand by that judgement.