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Republican leaders in the Senate are keeping a close eye on the health conditions of two senior members — John McCain of Arizona and Thad Cochran of Mississippi — ahead a crucial vote on the GOP tax plan next week.

Both have missed votes this week, though party leaders expect the two senators to be in position to vote for the tax bill, which could happen as early as Monday.

McCain, who announced he had brain cancer this summer, was hospitalized this week “for normal side effects of his ongoing cancer therapy,” his office said in a statement Wednesday night.

“Senator McCain looks forward to returning to work as soon as possible,” the statement said, though it did not include any details on the timing of his return.

Cochran had “an outpatient procedure Monday afternoon to address a non-Melanoma lesion on his nose,” his spokesman Chris Gallegos told CNN. “The procedure was more extensive than expected, but the senator is doing well and available now for votes if needed.”

“Senator Cochran is in Washington and expects to vote for the tax plan when it comes to the Senate next week,” Gallegos added.

Cochran has had health issues throughout the fall, including a urinary tract infection that kept him out of office for several weeks in October. At the time, Cochran said he thought he was physically fit for office.

Republicans hold a slim majority in the chamber — 52-48 — and losing three votes would block their plans to overhaul the US tax system.

GOP Sen. Bob Corker of Tennessee voted against the Senate bill when it initially passed the chamber, though he has not said whether he’ll vote against final passage of the bill hammered out between the House and Senate.

Republicans have a very tight deadline to pass tax reform next week, with a long and pressing list of year-end actions they are planning to complete before leaving town for the holiday.