WASHINGTON — Several former Obama administration officials were on their regular Wednesday morning conference call this week, plotting against Republican efforts to repeal the Affordable Care Act, when Tom Price, the secretary of health and human services, said on CNBC that his party should shoot for “the lowest common denominator” on health care.

Within moments, the former president’s associates had blasted out Mr. Price’s comments to Capitol Hill and beyond, accusing President Trump and his Republican allies of another “scheme to repeal health care” developed in a “secret back room filled with the most extreme anti-health care voices in their party.”

As Senate Republicans make a final, urgent push this week to repeal the law they deride as Obamacare, they face a fierce and sophisticated opposition campaign by scores of former Obama administration officials working overtime to prevent Mr. Trump from gutting the policy they helped create.

Motivated by the assault on President Barack Obama’s top domestic achievement, many of his former aides and allies have put aside family vacations and deferred new careers to participate in what has become a reunion of sorts to save the Affordable Care Act.