Facing a revolt from both his right and left flanks, House Speaker Paul Ryan is trying to unite the Republican Party behind his Obamacare replacement plan by promising that the current House bill will be just the first of several pieces of legislation that will remake the U.S. health-care system. But the reality is that if passing Part One of Ryan’s vision is difficult, Parts Two and Three may be virtually impossible.

Republicans can use the process known as budget reconciliation to repeal the Affordable Care Act and lay the framework for their replacement legislation with a simple party-line vote. As Ryan has noted, reconciliation can only be used for provisions that have a significant impact on the federal budget—such as the Obamacare taxes and subsidies. But later stages of the overhaul—including the conservative alternative to the individual mandate, which is the linchpin of the House plan—will have to go through the traditional legislative process, which means they will require 60 votes to pass the Senate.

According to Ryan and Health and Human Services Secretary Tom Price, the second phase will focus on rolling back Obamacare regulations and the third will involve the introduction of additional health-care legislation at some point in the future. Or as one conservative activist characterized it to Politico, “These are three planes leaving Casablanca—it’s not a panic.”

Unfortunately for Ryan and Donald Trump, planes number two and three will require at least eight Democratic senators on board to have any chance of takeoff. And with G.O.P. leadership already straining to convince enough conservative Republicans to back the House plan, getting Democrats to break ranks too seems like an impossible task. But the G.O.P.’s plan depends on it. As Connecticut senator Chris Murphy noted on Twitter, the “linchpin” of Trumpcare is the “continuous coverage” provision, which requires insurers to charge individuals a 30 percent surcharge on their premiums if they let their coverage lapse. The replacement to Obamacare’s individual mandate, which Republicans derided for years, the penalty is essential to the G.O.P. plan, or in Murphy’s words, “Bill falls apart without that provision.” And as it is a regulation that does not impact the budget, it needs 60 votes to pass. Similarly, Trump’s promise to allow individuals to purchase insurance across state lines also hinges on Democratic cooperation—a reality, it seems, the president has yet to grasp.

During a closed-door meeting with conservative activists earlier this week, Trump reportedly informed the group that another health-care bill is expected to be introduced in the House as early as next week, to jump-start the latter phases in the health-care overhaul. But the conservatives in the room were skeptical of Trump’s confidence that the bill would survive the House. “It was classic Trump style. He said phase three they should vote on next week, and everybody in the room knew that was unlikely,” one attendee told the Washington Examiner. Another individual who attended the meeting echoed that sentiment. “I told him to have [Senate Majority Leader Mitch] McConnell jump in and get the vote scheduled. He kind of looked at me when I said that, digested it, and the staff kind of jumped in,” the source told the Examiner, adding, “Honestly, I think the real timetable [for phases two and three] is a few months later when it sinks in that Obamacare has been repealed and Democrats might be willing to cut a deal of some sort.”

Unlike Trump, the conservatives were keenly aware of the difficulties ahead for the G.O.P. with its three-step approach. “If you don’t get competition across state lines in the first bill, the insurance industry is going to be popping champagne everywhere knowing that they can stop the next bill,” another source in the room lamented. “That is the big battle here. The big winner or loser is the health insurance industry, who I think drafted most of this bill.”

On Thursday, Trump asserted on Twitter that Trumpcare will “end in a beautiful picture.” But the truth is that, despite G.O.P. majorities in both houses of Congress and him in the White House, without Democratic support—it might not happen at all.