Republicans expressed cautious optimism Monday that Sen. John McCain John Sidney McCainBiden's six best bets in 2016 Trump states Replacing Justice Ginsburg could depend on Arizona's next senator The Hill's Morning Report - Sponsored by Facebook - Washington on edge amid SCOTUS vacancy MORE (R-Ariz.), who was diagnosed with brain cancer last week, will return to the Senate in time for a key ObamaCare repeal vote on Tuesday.

The final decision rests with McCain’s doctors.

The 80-year-old lawmaker underwent an emergency craniotomy last week to remove a blood clot above his left eye. He was later diagnosed with a glioblastoma, an aggressive form of cancer.

Senate aides reported last week that McCain was alert and talking to staff shortly after the operation and eager to return to Washington.

But medical experts at the Mayo Clinic Hospital in Phoenix may not like the idea of him jumping back to work so soon.

ADVERTISEMENT

Senate Republican Whip John Cornyn John CornynTumultuous court battle upends fight for Senate Texas Democrats roll out first wave of planned digital ads as Election Day nears Calls grow for Biden to expand election map in final sprint MORE (Texas) told reporters Monday that McCain was trying to get approval from his doctors to return Tuesday.

But Sen. John Thune John Randolph ThuneGraham: GOP will confirm Trump's Supreme Court nominee before the election Tumultuous court battle upends fight for Senate What Senate Republicans have said about election-year Supreme Court vacancies MORE (S.D.), the chamber’s third-ranking Republican, said "I don't expect it" when asked if McCain would be there Tuesday.

McCain’s office declined to confirm his schedule.

Two Senate aides said they expect he will be present Tuesday afternoon when lawmakers vote on a motion to proceed to the House-passed American Health Care Act.

Senate Majority Leader Mitch McConnell Addison (Mitch) Mitchell McConnellGraham: GOP will confirm Trump's Supreme Court nominee before the election Trump puts Supreme Court fight at center of Ohio rally The Memo: Dems face balancing act on SCOTUS fight MORE (R-Ky.) has said he will offer an amendment to replace it with a bill that repeals as much of ObamaCare as possible, setting up a two-year transition to craft replacement legislation.

If that amendment fails, the Senate is likely to move to its own version of legislation to repeal and replace the pillars of ObamaCare, the Better Care Reconciliation Act. That measure, however, did not appear to have enough votes to pass as of Monday afternoon.

The legislation will move under special budgetary rules setting up 20 hours of debate and rapid-fire votes on an indefinite number of amendments, a grueling schedule even for a lawmaker in fine health.

—Peter Sullivan contributed. Updated at 5:48 p.m.