WASHINGTON — (CNN) It will take more than a devastating diagnosis to keep John McCain out of the heat of political battle.

The Arizona senator makes a poignant return to the Senate on Tuesday, less than a week after learning he has an aggressive form of brain cancer, just in time to boost tricky GOP vote math on the wobbling bid to replace Obamacare.

McCain’s return comes as he considers treatment options for the latest fight of a lifetime of military heroism and political combat that has made him one of America’s most enduring public figures.

There will likely be emotional scenes when the grizzled Senate warrior arrives amid his colleagues in the chamber, following a rare bipartisan outpouring of shock and sympathy for the 80-year-old former presidential nominee.

His quick return, after securing the permission of his doctors to make the long cross-continental flight, fits the character of a senator who still keeps a frenetic schedule that would humble a younger man, and has shown he has no interest in retirement.

McCain is likely to greet fanfare that will pay tribute to his reemergence with the same gruff humor that has been a trademark of his career, though he has spoken in the past about his desire to make the most of every day he has left in the Senate.

“Look forward to returning to Senate tomorrow to continue work on health care reform, defense bill & #RussiaSanctions,” McCain tweeted Monday.

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But for all the sentiment expected on Tuesday, the hard business of politics in polarized Washington is likely to quickly reassert itself.

That’s because McCain’s arrival will also underscore the fierce partisan nature of the health care debate. The Arizona senator has long been an opponent of the most cherished domestic achievement of the man who beat him to the White House in 2008. And he is likely to ease Senate Majority Leader Mitch McConnell’s plight by voting to begin debate on a health care bill.

McConnell can afford to lose no more than two votes from his 52-member conference to advance to a debate on health care reform or to pass a final bill.

McCain’s absence had made that equation even tougher, though given opposition to the current health care legislation from both the left and right of the party, McConnell’s task still looks daunting.
It also remains unclear whether McCain would go along with a full repeal bill if that is what emerges from the current GOP confusion over how to tackle the issue.

McCain even criticized a repeal and replace effort during his absence in Arizona, calling on the GOP to open talks with Democrats on how to fix a growing health care crisis.

“As this law continues to crumble in Arizona and states across the country, we must not repeat the original mistakes that led to Obamacare’s failure,” he said in a statement last week.

“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.”

As his tweet made clear, McCain is not just returning to Washington to debate health care.

If the vote fails, the Senate is next expected to take up the National Defense Authorization Act, according to two congressional aides.

That bill is the product of the Armed Services Committee, which McCain leads and as such, he would pilot debate on the measure on the Senate floor.

He has also been a key figure in the debate over new sanctions to punish alleged Russian meddling in last year’s election. President Donald Trump has yet to say that he will sign the bill.

McCain’s diagnosis last week with a glioblastoma tumor, an aggressive form of cancer, shocked Washington, where he has friends across the aisle — even among lawmakers who do not share his conservative Republicanism.

Average survival for malignant glioblastoma, a condition that claimed the life of former Democratic Senate lion and McCain friend Ted Kennedy, tends to be around 14 months with treatment, that includes chemotherapy and radiation.

Still, one 2009 study reported that almost 10% of patients with glioblastoma may live five years or longer, according to the American Brain Tumor Association.

During the weekend, McCain’s daughter Meghan tweeted a photo of her and her father. They were hiking together in the Arizona sunshine.

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