 -- Senate Majority Leader Mitch McConnell is hoping to send Senate Republicans home for the Fourth of July recess with a revised version of their health care bill, but it remains unclear if he can bridge the deep divides over the bill in his own party.

“Senator McConnell’s goal is to finish our work by this week so we can get an estimate from the CBO about the final cost of the bill, then we’ll be able to vote on it in July,” Sen. Lamar Alexander said.

With at least nine GOP Senators still opposed to the bill, having concerns that span the ideological spectrum, it’s unclear which aspects of the draft McConnell can change to get the 50 votes he needs for it to pass.

“That is an existential question,” Sen. Bill Cassidy told ABC News. “And it’s very hard for me to answer existential questions. Right now there’s still kind of, ‘can we do it?’ And I can’t answer that. I just can’t.”

“I’m totally optimistic. I think everything’s settled,” said a clearly sarcastic Sen. John McCain.

Even the no votes, who would presumably be getting the most courting, don’t know what’s on the negotiating table.

“I don’t know what the [majority] leader’s going to come up with this round. And there are a lot of different interests that he's trying to accommodate,” said Sen. Susan Collins.

Who wants what?

Senators who have staked out a relatively moderate position on the bill, most of whom come from states that expanded Medicaid under the Affordable Care Act, are concerned that the bill as written would cause too much harm to recipients in their states.

Still other moderates, like Collins, oppose the bill’s scrapping of federal funding for Planned Parenthood. Collins told reporters Tuesday that it will take fundamental changes, not just tweaks, to get her on board.

Conservatives, like Sen. Ted Cruz, on the other hand, want insurers to be able to opt out of covering essential health benefits, required under Obamacare, like maternity and mental health care. Cruz has an amendment, which he pitched again during an all-Republicans lunch meeting Wednesday, that would allow insurers to scrap those coverage requirements so long as there is one plan available in each state that is ACA-compliant.

“It expands options for consumers, it expands the freedom of consumers to purchase more affordable plans, and I would note that there are a host of other plans we have discussed,” Cruz explained.

Other conservatives, like Sen. Rand Paul, are fixated on scrapping the tax credits to help consumers pay for insurance, which is a fundamental part of both the House and Senate plans. It’s the sort of major structural change that faces tough odds to make it into the final bill.

New bill, new score

Even if Republicans can come up with a new version by the end of the week it will still have to be re-scored by the Congressional Budget Office, which could take several days at least. It’s also possible many Senators could reserve judgment until they see a revised score.

“The leader said he wants the talks to continue throughout the week. I'm sure we'll be having lots of back and forth with CBO in the coming weeks,” a spokesman for McConnell said.

“He's going to try to come up with something and we're close enough that we can do that, maybe even an agreement,” Sen. Jim Inhofe said. “But it would not be any good because then we have to get a re-scoring of it and that's where the additional 10 days come in.”

Plan B(ipartisan)

If Senate Republicans can’t get something done this week, some members suggest it may be time for Plan B.

“If for some reason it fails ... the floodgates would probably open to reach a bipartisan compromise,” Sen. Shelley Moore Capito said on CNN this morning.

One option might be to do a more piecemeal bill that offers insurance companies some reassurance that the market isn't going to be on a roller coaster ride for the next few years as Congress continues to sort out these existential questions.

“You gotta do something sooner or later because people are losing access to insurance,” said Sen. David Perdue, who wasn't against or even citing concerns about the original Senate draft.

Even Rand Paul has suggested that leadership break the Republican bill into pieces, so moderates could work with Democrats on some areas, like market stabilization, and conservatives on others.

“I’ll vote for a more narrowly structured repeal bill – and the big-government items the moderates want, they can still get ‘em. They can put it in a bill that the Democrats love,” Paul said.