a human figure made of straw and placed in a field to frighten away birds; a straw man

a last hope or desperate resort that usually fails to solve the problem; something one relies on in a crisis that is ultimately ineffective

To try desperately to find help or hope in a hopeless situation, like a drowning person grasping for straw.

the straw that broke the camel's back; an idiom for a seemingly minor thing that causes a final collapse after many other burdens or problems