Republicans have 52 seats in the Senate. They can lose two votes, leaving Pence to break the tie. They need to follow the principle of the "minimal winning coalition," which I covered the last time I addressed this issue. Go for precisely 50. That means giving up on Collins and Murkowski. If they have Portman and Capito, they probably have Gardner. The trick is splitting up Collins and Cassidy. I'll address that later, but it should be possible at this point, now that Portman and Capito have caved. We should treat those three as a voting bloc.
Essentially, Portman and Capito agreed to phase out the Medicaid expansion, but just at a slower rate than the House bill. Substantively, it's still a cave. That is very important. It suggests that there isn't much willingness to fight the hardliners here. Remember, these are the ones who took the strong, public stance, breaking from the commitment they took publicly. The ones who have been more wishy-washy in public are even more likely to fall in line. The question is whether the hardliners will accept the slower phase-out of Medicaid. I'd bet they do. So, what's left to stop the repeal?
Senate rules. Getting the Freedom Caucus to agree to anything required repealing Obamacare regulations on what insurance companies must cover (the pre-existing conditions, "essential benefits," that type of stuff). Remember, Republicans are using "budget reconciliation" to do this without any Democratic votes because a reconciliation bill can't be filibustered, but according to the Byrd Rule, reconciliation bills can't contain non-budgetary provisions. The Senate parliamentarian is likely to look at any provisions about regulation changes and repeals and declare them non-budgetary. The Senate then has a couple of options:
1) Go nuclear, in some form (I'll get to that)
2) Pass a bill that the Freedom Caucus won't accept
3) Give up
It is looking like the Portman/Capito/Garder faction is falling in line. If the hardliners accept a slower Medicaid phase-out (likely but not definite), that was one of the biggest obstacles to passage. The last remaining coalition obstacle is breaking up the Collins-Cassidy pair. Once Republicans manage that, they hit 50. Again, assuming the hardliners accept a slower phase-out of Medicaid.
This is the policy substance, coalition-building stuff, though.
The Byrd Rule is in the hands of the parliamentarian, not a bunch of partisan Republicans. That's a whole different game. It isn't subject to the same processes at all.
