Democrats and their allies in the health-care advocacy community have taken notice, sounding alarms in a bid to mobilize the same level of opposition to the new bill as they were able to do successfully against previous GOP proposals.

“This is a red siren moment for the entire country,” Senate Minority Leader Charles Schumer said at a press conference Monday. “If this bill becomes law, our health-care system will be dramatically curtailed, and there will be chaos in many states.”

The Graham-Cassidy bill would repeal Obamacare’s individual and employer mandates for health insurance but differs from some earlier proposals by keeping most of the law’s tax increases. That revenue is then converted into a block grant for states, which could choose how to use it to best fit their needs. Graham and Cassidy are trying to appeal to the conservative preference for federalism and attract the support of governors by offering them maximal flexibility. They could keep Obamacare’s standards and requirements, or they could ditch almost all of them, including some of the protections intended for people with preexisting conditions. But as my colleague Vann Newkirk explains, the proposal is not as much of a compromise as it might appear to be, since the measure scales back funding for Medicaid over time, and the states that would be most likely to keep Obamacare’s structure would receive substantially less money from the federal government.

According to Cassidy, the bill has the private support of 49 GOP senators, putting it, again, just one vote shy of the 50 needed to clear the Senate under the budget reconciliation rules that expire at month’s end and that allow Republicans to avoid a Democratic filibuster. Cassidy’s rosy claim is impossible to verify, because plenty of GOP senators have said little or nothing publicly about the proposal. But even if it were true, the 50th vote has always been the hardest for the party to get, and it’s unclear what in the Graham-Cassidy proposal would secure the backing of either Senator Lisa Murkowski of Alaska or McCain—two of the three senators who opposed the last repeal proposal in July.

Already, two of the 52 Senate Republicans appear to be out of reach for Graham and Cassidy. Senator Rand Paul of Kentucky has declared the proposal to be “Obamacare lite” and debated its merits with Cassidy on Twitter. “Graham/Cassidy keeps Obamacare and tells the states to run it. No thanks,” Paul concluded Monday morning. Senator Susan Collins of Maine hasn’t taken quite as strong a stance, but she had opposed each and every one of the previous GOP repeal proposals and does not appear inclined to back this one.

“Senator Collins has a number of concerns with the Graham-Cassidy proposal, including the cuts to the Medicaid program and the impact to the requirement that insurers provide coverage to people with preexisting conditions,” Collins spokeswoman Annie Clark told me on Monday. “She will be examining the forthcoming CBO analysis.”