It is as well to know what developments are likely, or what is the state of
public opinion. ‘To know which way the cat is going to jump’ has much the same
meaning.

> ‘I’m going to make some inquiries,’ said the politician. ‘As soon as I know
which way the wind blows, I’ll decide which line I’m going to take. I’m not
going to be on the losing side if I can help it’