The Senate plans to vote Tuesday to try to advance a sweeping rewrite of the nation’s health-care laws with the last-minute arrival of Arizona Sen. John McCain (R), who could provide the critical vote to start debate on the bill even as he announced last week that he is suffering from brain cancer.

In a bit of drama, McCain said Monday night that he will return to the U.S. Capitol on Tuesday to vote on whether to start debate on the health-care bill. The senator had been recuperating from surgery in Arizona.

“Senator McCain looks forward to returning to the United States Senate tomorrow to continue working on important legislation, including health care reform, the National Defense Authorization Act, and new sanctions on Russia, Iran and North Korea,” McCain’s office said in a statement.

It is unclear, however, if McCain’s return will improve Republicans’ prospects of passing a key procedural hurdle to move the health-care bill forward. Senate Majority Leader Mitch McConnell (R-Ky.) has insisted he intends to hold a vote to start debate on health care on Tuesday — even though it’s prospects are murky at best.

The news that McCain would return to Washington came after a day in which President Trump took to publicly calling out Republicans in Congress for failing to achieve the rollback of the Affordable Care Act — something that both he and the GOP congressional majority have long promised to do. As of Monday evening, Trump’s thinly veiled barbs at those in his party had done little to secure more support for passing a health-care measure.

Speaking at a White House event on Monday night, Trump threateningly urged Senate Republicans to vote “yes” on a procedural motion that would allow debate on health-care legislation to begin. However, exactly what legislation lawmakers would be debating remained unclear to many of them late Monday.

In a West Virginia speech before the National Boy Scout Jamboree, Trump sought to pressure Sen. Shelley Moore Capito (R-W.Va.) by saying, “You better get Senator Capito to vote for it,” referring to his health and human services secretary, Tom Price, who was with him. Trump also quipped that he would fire Price if he did not round up enough votes.

“As the Scout law says, a Scout is trustworthy, loyal — we could use some more loyalty, I can tell you that,” Trump said in a day that was filled with thinly veiled barbs at Republicans who have failed to advance the health-care revamp.

McCain’s dramatic return could inject some suspense into the procedural vote to open debate, which so far has failed to pick up strength — no matter which version is considered.

Revered on both sides of the aisle, the news that McCain has brain cancer cast a pall over the Capitol last week and his return is sure to provide a morale boost for colleagues in both parties.

But most immediately, McCain may provide a critical vote in support of beginning formal debate on the health-care bill. Republican leaders openly discussed the possibility of McCain’s return with reporters on Monday during an evening vote.

“I’m pretty confident we’ll get on the bill even without John, “ Sen. John Cornyn (R-Tex.), the chamber’s lead GOP vote-counter, told reporters.

Sen. Susan Collins (R-Maine), said she spoke with McCain on Saturday and that her frequent collaborator was eager to get back to work.

“It is just extraordinary how upbeat he is and how accepting of his diagnosis — it was truly inspirational to talk with him,” she said. “I have a feeling that if there’s any way he can be back, he will be here — whether his doctors like it. It just reminds me of what an extraordinarily brave person he is.”

Without McCain, Senate Majority Leader Mitch McConnell (R-Ky.) could only have afforded one GOP defection. Multiple Republican senators have raised objections to each health-care proposal that has been offered, leaving McConnell and Trump in a very difficult spot.

“There is still time to do the right thing,” Trump said at the White House…