Sen. John McCain revealed over the weekend that he had surgery to remove a blood clot from above his eye (more on his condition below). As a result, he will not be returning to Washington this week -- and his absence has suddenly brought consideration of the Senate health care bill to a halt.

Reality check: This bill can't pass without McCain

Here's what McCain's absence does to McConnell's whip count: There were already two Senate Republicans who have said they would vote "no" on motion to proceed on this bill -- Sens. Rand Paul and Susan Collins. McConnell could not afford to lose one more senator.

McCain was a solid "yes" on the motion to proceed, and his sudden absence means that *even if* every other GOP senator got behind the legislation, McConnell would only have 49 "yes" votes. Do the math: 49 out of 99 is not a majority. In other words, if a vote were held this week, the bill would go down on motion to proceed.

McConnell will "defer" Senate bill

Leadership was pushing for a first procedural vote on the Senate health care bill for as early as Tuesday. That's no longer happening.

Here's what McConnell said in a statement late Saturday: "While John is recovering, the Senate will continue our work on legislative items and nominations, and will defer consideration of the Better Care Act."

No word from leadership on when a vote would be rescheduled for -- if ever.

Another programming note: No CBO score

We were expecting an updated score from the Congressional Budget Office on the revised Senate bill today. That is also not happening , a GOP Senate aide told CNN on Sunday. No guidance from aides or the CBO on when we'll see that score.

There's some chatter that the delay in the vote may now give the CBO time to score Sen. Ted Cruz's amendment -- a key provision added to the bill that won over Cruz and may help bring on board others. (More on that below)

The big picture: So much is up in the air

It's hard to overstate right now just how uncertain the fate of this health care bill is.

Speaking to Republican staffers over the weekend, nobody really has a firm idea of when McCain will be back -- it's far from a guarantee that he'll be back after this week. So there is trepidation about the timeline for the health care bill, since McConnell really can't move forward without McCain's "yes" vote.

And it's not just the health care bill: the Senate floor schedule is unclear now that health care is on hold. McConnell announced the Senate would delay August recess until the third week of the month to finish health care, then tackle backed-up nominations, the reauthorization of the Food and Drug Administration, and the annual defense policy bill. That last bill can't get done with McCain out, since he's the armed services committee chairman who must manage the bill on the floor.

But this week will give senators extra time on nominations and to consider government spending bills and a debt ceiling increase, the deadline for which is now October.

Is McCain doing OK?

His office said Saturday that the senator is "resting comfortably at home and is in good condition."

His doctors also said the surgery went "very well," and the 80-year-old Vietnam War veteran was described as being in "good spirits."

A brutal weekend for the health care bill

The McCain news aside, this was kind of a devastating weekend for the Senate bill. CNN's Eric Bradner reported from Rhode Island over the weekend that the National Governors Association had its summer meeting -- and health care was front and cente r.

The governors were particularly worked up about what the Senate bill would do to Medicaid in their states. Vice President Mike Pence, Health and Human Services Secretary Tom Price and Seema Verma , the administrator of the Centers for Medicare and Medicaid Services, were all present to reassure the governors, but it's clear that many of them are still largely skeptical at best.

We even saw Ohio Republican Gov. John Kasich's office publicly objecting to what Pence said at the NGA gathering about Medicaid in Ohio -- not exactly a sign of everyone coming together.

JUST WATCHED Collins takes issue with Pence on Medicaid Replay More Videos ... MUST WATCH Collins takes issue with Pence on Medicaid 01:25

Key senators to watch

One optimistic way to view the vote delay is that it now gives some of the wavering and undecided GOP senators more time to think and negotiate. But getting these senators on board remains a tough task -- their concerns about Medicaid are grave, and what they would like are changes to the base bill (as in, they're unwilling to just settle for a promise from McConnell that they could just offer up amendments on the Senate floor).

Rob Portman of Ohio

Shelley Moore Capito of West Virginia

Dean Heller of Nevada

Lisa Murkowski of Alaska

All four of them remain undecided. All of them expressed concerns about how the revised plan, which would make significant cuts to Medicaid and affect low-income people in their states.

One important caveat: Even if McCain comes back next week, McConnell still can't afford to lose one more senator. That means *any* GOP senator can be the deal-breaker.

For example: Sen. Mike Lee, a conservative Republican from Utah, is still undecided as of Sunday afternoon.

Will the Cruz amendment survive a Byrd bath?

Two GOP sources familiar with the matter told CNN's Manu Raju last week that they don't expect the all-important Cruz amendment to get an official score from CBO (this was all before we learned Sunday that there won't be a CBO score on Monday after all).

Instead, the amendment will be scored by HHS, which is unusual because HHS is pushing for the bill's passage and not an independent arbiter like CBO is.

Democrats plan to make a vocal argument against inclusion of the Cruz amendment because of this.

The GOP sources expect the Cruz amendment may have to be stripped on the floor because it does not meet the strict rules required during the budget reconciliation process. That means it is possible that -- even if 50 senators vote to get on the bill -- the Cruz amendment will get killed on the floor, which could cost them votes on the right.

The question now is whether the Cruz amendment will now be scored by the CBO, given that a vote on the bill has been delayed.