straw vote

Also, straw poll. An unofficial vote or poll indicating how people feel about a candidate or issue. For example, Let's take a straw poll on the bill and see how it fares. This idiom alludes to a straw used to show in what direction the wind blows, in this case the wind of public opinion. O. Henry joked about it in A Ruler of Men (1907): "A straw vote only shows which way the hot air blows." [c. 1885]