McCain bucked his party once. Will he do it again?

Sen. John McCain bucked his party – and his President – in the most extraordinary fashion this summer.

Not even two months later, the Arizona Republican finds himself confronting perhaps an even tougher dilemma: The possibility of once again defying his GOP colleagues, including his closest friend on Capitol Hill, and casting another potentially decisive vote that prevents Republicans from achieving their years-long campaign pledge to repeal Obamacare.

McCain’s dramatic “no” vote in July – along with opposition from Sens. Lisa Murkowski of Alaska and Susan Collins of Maine – killed a Senate Republican bill to repeal Obamacare. At the time, the veteran senator made an impassioned speech on the Senate floor, pleading with his colleague to return to doing business through “regular order” – holding hearings and working with Democrats across the aisle.

“Let’s trust each other,” McCain said. “Let’s return to regular order. We’ve been spinning our wheels on too many important issues because we keep trying to find a way to win without help from across the aisle.”

Now, the latest campaign to repeal Obamacare that many Republicans in Washington believed was dead has suddenly come roaring back. Leading that effort: Sen. Lindsey Graham, the South Carolina Republican – and McCain’s best friend.

The legislation, co-sponsored by Sen. Bill Cassidy of Louisiana and known as Graham-Cassidy, would gut the Affordable Care Act, turning Obamacare’s subsidies into block grants, doing away with Medicaid expansion and slashing further funding to the program.

WHIP LIST: How Republicans say they’ll vote on the Graham-Cassidy health care bill

States that expanded Medicaid, such as Arizona, are likely to see their funding reduced under the Graham-Cassidy proposal. The state would get $1.6 billion less from the federal government in 2026 because of reduced support for Medicaid and Obamacare’s premium subsidies, according to the left-leaning Center on Budget and Policy Priorities.

Another hangup for McCain: Republicans are attempting to push the bill through once again through the budget reconciliation protocol, which would allow the legislation to pass with solely 50 votes (plus the tie-breaking vote of the vice president) as opposed to the 60 votes that would be needed to break a filibuster. That means this proposal would only need – and get – Republican support.

McCain, who is battling an aggressive form of brain cancer, has been railing against the very process for weeks, urging Republicans to start over with a bipartisan approach and hold plenty of hearings and debates.

McCain oozed with sarcasm Tuesday afternoon when asked about the Senate finance committee’s decision to hold a last-minute hearing on Graham-Cassidy next week.

“I’m glad to hear that. That’s wonderful news. Ta-da!” McCain said, before proceeding to play an imaginary trumpet with his fingers.

Pressed on whether one hearing counts as “regular order,” McCain quipped at a CNN reporter: “Do you think that that’s regular order?”

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“I always thought regular order was hearings and debates and amendments and into the floor with debates and discussion and amendments! That’s what I thought regular order was,” McCain said.

Echoing what he had said during the deliberations over the last GOP bill, McCain said Tuesday that he would only support the new plan if he received “enough assurance that the bill would help my state of Arizona.”

Asked an obvious question – whether he had spoken with Graham about the proposal – McCain simply said: “I talk to Lindsey Graham constantly, unfortunately.”

CNN’s Tami Luhby contributed to this report.