Almost all political stories from Russia include a ritual sentence that says polls show Putin is highly popular, but aren’t such polls meaningless in a society where ordinary people are now afraid to say anything against Putin to a stranger? Isn’t Putin’s true popularity undeterminable under present circumstances ?

I don’t necessarily agree that people are afraid to criticize Mr. Putin to a stranger.
The nature of dissent here is more nuanced than that. Newspapers and the Internet are filled with criticism of Mr. Putin.

The Kremlin has, however, eliminated criticism of the president in the most powerful mass medium, television.
It also seems as if there is a policy of punishing prominent people for publicly opposing Mr. Putin.
In other words, if you want to be very successful in Russia – in business or the arts, for example – don’t speak out against the Kremlin and don’t help the opposition. If you do, you might suffer. The average person doesn’t typically face such pressure. I’m not saying that it does not occur, just that it is not widespread.