When the year began, Senate Majority Leader Mitch McConnell's number one priority was to quickly move forward with a plan to repeal Obamacare—but in a way that delayed the repeal while the GOP settled on some sort of replacement plan.

That plan came with many potential pitfalls, and now it looks as if it may not work out after all—thanks in large part to opposition from Sen. Rand Paul (R-Kentucky).

McConnell's intention was to use the reconciliation process, which allows the Senate to pass certain types of bills that are directly relevant to the budget with a simple majority, to strip out certain key components of the law, including its individual mandate, taxes, and insurance subsidies. Those changes, however, would not go into effect for somewhere between two and four years. During that time, the hope was that Republicans in Congress would finally work out some sort of replacement plan.

The problem with this plan was that it was bound to create uncertainty and disruption in the individual insurance market. And Republicans, who have failed for years to unify around a replacement plan, might never actually coalesce around an alternative, leading to more instability and the possibility that the delay would be extended for years.

Last week, however, Rand Paul declared that he opposed repeal without a ready substitute. "I think it's imperative that Republicans do a replacement simultaneous to repeal," he said on MSNBC.

Paul now seems to have support for his position from none other than President-elect Donald Trump. Paul said today that he received a call from Trump indicating that the incoming president supported a simultaneous repeal and replacement. "[Trump] called after seeing an interview that I had done [talking about] that we should vote on Obamacare replacement at the same time," Paul told Politico.

Paul isn't the only GOP senator to express wariness about the repeal and delay plan. As Politico's Dan Diamond noted this morning, Sens. Lamar Alexander, Susan Collins, Bob Corker, and Tom Cotton have all warned of the perils of repealing the law without a replacement. Given how slim the GOP's majority is in the Senate, that's potentially enough votes to put the brakes on any repeal and delay legislation. Trump siding with Rand Paul on the necessity of a simultaneous replacement makes McConnell's original strategy even more difficult.

That's presuming, of course, that this is what Trump actually believes, and that his administration would actually oppose repeal and delay legislation. Senior Trump aides Kellyanne Conway and Reince Preibus hedged on that point when asked on CNN, declining to commit to any particular course of action.

So it's still not entirely clear where the Trump administration stands on the repeal process. And even if they did back Paul in insisting on a simultaneous replacement, it's not clear how that would work out either. Republicans in congress have had years to unify around a replacement plan, but have never been able to do so. When pushed on the question, Mitch McConnell's office is being tellingly vague about what a replacement might entail.

Rand Paul is right to worry about the political and policy problems with the repeal and delay strategy, and one hopes that his stance will force other congressional Republicans to finally do what they have so far refused—and actually commit to wrestling with difficult questions about what their health policy goals are and what sort of tradeoffs they are willing to accept.