Eliza Collins

USA TODAY

WASHINGTON — Senate Majority Leader Mitch McConnell, R-Ky., is still expected to hold a vote to proceed on some form of legislation to repeal Obamacare next week, despite the fact that Sen. John McCain likely won’t be back in Washington to cast his vote.

The Arizona Republican senator's absence, in addition to the GOP members who have announced their opposition to the bill, makes it even harder for McConnell to round up the votes to pass a bill.

McConnell’s spokesman David Popp told USA TODAY on Thursday that the vote is still on despite the news Wednesday night that McCain has been diagnosed with brain cancer. McCain is currently reviewing his treatment options back in Arizona, and it is not clear when he will return to Washington. Senate rules require that a lawmaker be at the U.S. Capitol in order to cast a vote.

Despite frustration about the closed-door process GOP leadership took in drafting the health care legislation, McCain was not expected to be one of the lawmakers blocking a bill. Republicans hold such a narrow majority, 52-48, that even with McCain’s vote they can only lose the votes of two senators and still pass a bill.

So far, four GOP lawmakers have said they will vote against the Senate bill to repeal and replace Obamacare, also known as the Better Care Reconciliation Act.

Three senators have also announced opposition to an alternate plan that would repeal Obamacare without a replacement, designed to force Democrats to the table to negotiate a replacement down the road.

As of Thursday afternoon, it was still not clear which of the bills would be brought up for a vote.

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Asked by reporters whether there is an agreement on what version of the health care bill will be voted on next week, Sen. Bill Cassidy, R-La., replied, “Simple answer — no." At least a dozen other senators at the Capitol on Thursday were also unclear about what the final legislation would look like.

“We need to get on the bill to debate further,” Cassidy said, referring to the "motion to proceed" vote, which would bring the bill to the floor for discussion. But that motion requires 50 votes, and even Cassidy would not confirm that he would vote to bring the bill up. “We don’t know how things are set up yet.”

McCain’s expected absence means there is one less person who will vote with Republicans on either plan.

“We’re really working to try to get agreement (on health care) but obviously, yeah, it’s more challenging” to pass legislation without McCain, Sen. John Hoeven, R-N.D., told reporters Wednesday night as he left a gathering of GOP lawmakers who were trying to hash out differences on the health care bill. Hoeven said the group got news of McCain’s diagnosis when they were in the meeting.

Sen. Orrin Hatch, R-Utah, a member of GOP leadership, told reporters Thursday that he wasn't sure how to get a bill that satisfied everyone, particularly in light of McCain's absence. But he said it was possible.

“If we can get everybody to cooperate,” legislation can pass next week, Hatch said.

"I'll let the leadership make that decision," Sen. Mike Rounds, R-S.D., told reporters who asked whether Republicans should move forward to a vote even without McCain in attendance. "But you never know about John, he may be on his way here right now — you never know," he added.

In a tweet Thursday morning, McCain promised a speedy return.

If McCain does choose to continue to work, he won't be the only member of Congress to return to the Capitol while receiving medical treatment.

Sen. Frank Lautenberg, D-N.J., was 86 when he was diagnosed with stomach cancer in February 2010. He returned to Washington the following month and continued to vote and attend hearings while getting chemotherapy regularly for three months, usually on Fridays when votes were not held.

Lautenberg took part in a marathon round of 28 consecutive floor votes on the final legislative piece of the Affordable Care Act that began at 5 p.m. on March 24 and ended and 2 a.m. the next day.

At age 75, Sen. Arlen Specter, D-Pa., chaired the Senate Judiciary Committee during contentious hearings on the 2005 nomination of John Roberts to be Supreme Court chief justice just weeks after completing chemotherapy for Hodgkin’s disease.

Rep. Debbie Wasserman Schultz, D-Fla., had seven surgeries over the course of a year for breast cancer while continuing to manage the House Democrats’ 2008 campaign to capture Republican-held seats and serving as a surrogate speaker for President Obama’s re-election campaign. Wasserman Schultz, 43, did not reveal the cancer until after the treatment ended in March 2009 because she wanted to avoid upsetting her children, aged 8 and 4, and to prevent colleagues from treating her differently.

Contributing: Herb Jackson and Ledyard King