House Budget Committee Chairman Paul Ryan (R-Wis.) delivered a strong defense of Speaker John Boehner’s (R-Ohio) fiscal Plan B on the floor of the House on Thursday.

Hours before it is set to come to a vote, Plan B appears to be in deep trouble.

The bill extends most tax rates but allows them to rise on incomes of more than $1 million next year. Many conservatives are balking, and The Hill has identified at least 25 “no” or “lean no” votes. Boehner can only afford 24 defections to pass the bill with only Republican votes.

Ryan’s backing of the bill is seen as crucial to any chance it has of passing.