If you describe someone as whistling in the wind, you mean that they are trying unsuccessfully to change something which cannot be changed.
The leader of the Liberal Democrats accused the Prime Minister of whistling in thewind to raise Conservative party morale.
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whistle in the wind
to say something empty or pointless.
Prior to going out, he had confided to some Spanish journalists that he was goingto win the tournament, but that turned out to be whistling in the wind.