By Jordain Carney and Alexander Bolton - 07-21-17 06:00 AM EDT
Sen. John McCain's absence from Washington is throwing an already embattled GOP agenda further into limbo.
The Arizona Republican's diagnosis of brain cancer shook political Washington - where the 80-year-old senator is deeply respected by both parties - and sparked an outpouring of support from friends and political opponents alike.
While the focus has been on McCain's health, his absence also has repercussions for the Republican effort to repeal ObamaCare.
Majority Leader Mitch McConnell (R-Ky.) has a slim 52-seat majority with McCain. Without him, he can afford to lose just one vote in a procedural motion to start debate.
"We're really working to try to get agreement but obviously yeah it's more challenging without him," said Sen. John Hoeven (R-N.D.).
McCain, who was not in Washington this week after having a blood clot removed from above his left eye, may return.
In a tweet on Thursday, he quipped that "unfortunately for my sparring partners in Congress, I'll be back soon, so stand-by."
The Mayo Clinic, which performed McCain's surgery, said additional treatment could "include a combination of chemotherapy and radiation." His office added that McCain is in "good spirits" and believes any treatment will be "effective."
"Further consultations with Senator McCain's Mayo Clinic care team will indicate when he will return to the United States Senate," his office said.
GOP senators voiced optimism about an early return, but also appeared genuinely uncertain if that would happen.
"I hope he is able to come back next week but more than anything else we're all concerned about his well being and his recovery," said Sen. John Cornyn (R-Texas), the No. 2 Senate Republican.
Sen. Lindsey Graham (R-S.C.), a close friend and ally of McCain, said he would be back "as soon as he can." Meanwhile, Sen. Bob Corker (R-Tenn.) added that he hoped McCain would be "back soon."
GOP senators on Thursday suggested they were going forward with or without McCain.
"We can always come back to it if it is not successful, if we fail by one vote. ...So there is some benefit to going forward and seeing where we are next week, and that may well be the outcome," Cornyn said.
McConnell must corral competing Republican factions to win a healthcare victory.
Three GOP senators have said they are opposed to taking up the House bill if the endgame is to repeal ObamaCare with a delayed replacement. Four GOP senators oppose the Senate's last version of its repeal and replacement bill, known as the Better Care Reconciliation Act.
McCain, for his part, was undecided. Earlier this week, he had called for lawmakers to start over and have hearings.
"The Congress must now return to regular order, hold hearings, receive input from members of both parties, and heed the recommendations of our nation's governors so that we can produce a bill that finally provides Americans with access to quality and affordable health care," he said.
That was a break from GOP leaders, who have repeatedly warned that if they are forced to work with Democrats, ObamaCare will remain in place.
McCain, who is one of Trump's frankest critics in the Senate GOP caucus, is signaling that even if he isn't able to return to Washington, he won't sit on the sidelines.
He ripped the administration on Thursday over reports that it is shutting down a program arming Syrian rebels, noting the administration has "yet to articulate its vision" for the Middle East, including the years-old civil war in Syria.
"If these reports are true, the administration is playing right into the hands of Vladimir Putin," said McCain, the chairman of the Senate Armed Services Committee. "There is still no new strategy for victory in Afghanistan either. It is now mid-July, when the administration promised to deliver that strategy to Congress, and we are still waiting."
Sen. James Inhofe (R-Okla.) is expected to chair the committee's proceedings until McCain returns.
McCain's absence could also raise questions about the Senate's ability to pass the National Defense Authorization Act before the August recess.
McConnell pointed to the NDAA, which McCain is responsible for crafting, as one of the bills he wanted to take up when he announced that he was canceling the first two weeks of recess.
Cornyn said leadership is currently deferring to McCain on the bill, and Graham, a member of the Armed Services Committee, said "we'll take it up when he gets back."
Senate Republican Conference Chairman John Thune (S.D.) said leaders are unsure if they can still move the defense bill before the August recess.
Asked if the Senate is still on track to pass the defense bill before leaving town, Thune said "that's a good question."
Cornyn also hedged when pressed if Republicans were willing to wait for McCain even if it meant kicking the bill to the fall, saying they wanted to be "respectful."
"I think we just want to have that conversation. I'm not sure we've had that conversation with him yet," he said. "But we want to be respectful of him and his role as chairman of the committee."