(CNN) Democrats are finally back on the offensive on health care, brandishing an explosive new report stocked with damaging information about the Republicans' plans to repeal and replace Obamacare.

Their new ammunition: 24 million more Americans would be uninsured by 2026 under a House Republican proposal, while premiums would skyrocket for some of the most vulnerable Americans, including low-income elderly patients, according to analysis released on Monday by the Congressional Budget Office.

Democrats mobilized quickly on Monday to begin lobbing a stream of attacks against the Republican health care proposal, marking a drastic role reversal for a party that has struggled to defend the Affordable Care Act for the past eight years -- and suffered significant political losses along the way.

Particularly encouraging to Democrats is the CBO's conclusion that the Republican bill would hurt demographic groups that President Donald Trump tended to perform better with, including older Americans.

Sen. Bernie Sanders, the liberal independent from Vermont who challenged Hillary Clinton from the left in the 2016 presidential primary, was characteristically blunt: Thousands will "die," he said, if the GOP bill is passed.

"Throwing 24 million Americans off of health insurance, raising premiums for older low-income Americans, while giving $285 billion in tax breaks to the top 2% is a disgusting and immoral proposal," Sanders said. "Thousands of Americans will die if this legislation is passed and we have to do everything that we can to see that is defeated."

Senate Minority Leader Chuck Schumer said that Obamacare is becoming an asset -- not a liability -- for Democrats, even those running in red states that Trump won in November.

"That's because people realize by losing it they are going to be in real trouble," Schumer said.

The Democratic Congressional Campaign Committee is using the CBO findings to target vulnerable Republicans in the House -- particularly those who have already voted in support of the GOP legislation in last week's committee markups.

Between the Energy and Commerce and Ways and Means committees -- the two panels that approved the House GOP Obamacare bill last week -- there are at least a dozen Republican lawmakers that the DCCC view as beatable. The DCCC released a statement on Monday against one of those members: New Jersey Rep. Leonard Lance.

In an email titled, "CBO report shows Lance voted for healthcare bill that would leave 24 million more uninsured," DCCC spokesperson Evan Lukaske wrote: "Now Lance will have to own the consequences of voting for this disastrous bill."

Republicans had anticipated the CBO report would show that millions of people would lose coverage under the GOP proposal. Lawmakers and aides alike preemptively pushed back on the findings even before the CBO released its study, saying the loss of coverage would be due to people electing not to get insurance because they would no longer be mandated to do so.

But the loss in coverage is only exacerbated by other details in the CBO report.

Fourteen million fewer people would enroll in Medicaid by 2026 under the GOP legislation compared to under Obamacare. And while premiums on average are expected to decrease, there would be a steep premium hike for older people with lower incomes.

A 64-year-old making $26,500 would pay $1,700 for coverage in 2026 under Obamacare, thanks to its subsidies -- but under the Ryan plan, that person would get hit with a annual premium bill of $14,600.

"You've got to have a moral compass inside of ya. That's just not right," said Democratic Sen. Joe Manchin of West Virginia. "You can't do that and look at the elderly and look at the poor and look at the people that are addicted that need care. You just can't do that."

In public, GOP lawmakers and top administration officials vehemently questioned the credibility of the CBO's findings.

"We disagree strenuously with the report that was put out," Health and Human Services Secretary Tom Price said, arguing that the CBO report doesn't take into account other legislative changes that Republicans have proposed.

But in private, Republicans are on high alert.

"Oof," one Republican official supportive of the House GOP bill said. "We can recover, but this is not a good look."