Senate Majority Leader McConnell. Thomson Reuters Skeptical Republican senators bristled at the newly updated version of the Senate healthcare bill released Thursday morning, putting its future in doubt.

Almost immediately, two Republican senators came out against a procedural vote that would get the bill to the floor, meaning Senate Majority Leader Mitch McConnell and GOP leaders cannot afford to lose another vote.

A third GOP defection would prevent the bill from even being considered by the broader Senate and would most likely require the Better Care Reconciliation Act to be substantially overhauled — or scrapped.

Here's a rundown of the senators to watch in the debate and their current status on the vote: