beat the air
To keep doing something despite its apparent pointlessness or futility. There's no way he'll get his progressive agenda through—he's just beating the air.
beat the air
Also, beat the wind. Continue to make futile attempts, fight to no purpose. For example, The candidates for office were so much alike that we thought our vote amounted to beating the air . These phrases call up a vivid image of someone flailing away at nothing. [Late 1300s]