busted flush

noun2

1. •
   A potential flush which ultimately was not filled.

   • I thought I'd draw another spade, but I ended up with a busted flush.
2. •
   (UK) Anything which ends up worthless despite great potential.

   • If this [Tony Blair] is such an utterly busted flush of a leader, why are so many Tories and their outriders so keen to have this Prime Minister gone before he can fight another election? — 2004