Or more precisely, 15 that we know of since:
53 House Democrats supported this bill during the November 12th floor vote, in which it failed to get the 2/3rds majority needed to fast track it. All but 15 backed off, many under pressure from outraged constituents.
Dems as a party are beyond reform. But sure i'm down... let's introduce these 15 to pink floyds masterpiece first