catch at (a) straw(s)

To make a desperate attempt to salvage a bad situation. It's almost sad to watch how poorly that candidate is doing in the debate. He keeps bringing up his previous successes in every answer, but clearly he's catching at straws. A: "But what about all those times I took the trash out when you hadn't even asked me to?" B: "That has nothing to do with why you're in trouble now, so stop catching at a straw." The government is really catching at straws now in its attempt to defend the controversial legislation.