Repealing Obamacare with no replacement could be a 'recipe for disaster' In November, Trump promised to repeal and replace the law at the same time.

 -- President Trump this morning flipped on his previous strategy for accomplishing health care reform.

“If Republican Senators are unable to pass what they are working on now, they should immediately REPEAL, and then REPLACE at a later date!” he said in a tweet.

The president's new strategy was actually the preferred plan of attack for many top Republican lawmakers during the campaign.

Last November, just days after winning the election, Trump promised to repeal and replace the law concurrently.

“We’re going to do it simultaneously … we’re not going to have, like, a two-day period and we’re not going to have a two-year period where there’s nothing. It will be repealed and replaced,” he said during an interview with CBS.

Simply repealing parts of the law could leave insurance markets spinning, experts and some Republicans have warned.

Even The Heritage Foundation, a solidly right think-tank, cautioned in a February report that parts of the Affordable Care Act should be repealed gradually.

“Congress must replace Obamacare through a careful transition process that establishes everyone on more solid ground,” the report said. “Timing and sequencing of these efforts are complex, and proper execution is critical. Congress, the Trump Administration, and the states should work together both to ensure a smooth transition for the repeal of Obamacare.”

The Heritage Foundation, like other conservative groups, recommends an immediate repeal of the individual and employer insurance mandates. But it argued that rolling back the Medicaid expansion and government subsidies to help people buy individual insurance should take place a few years after any repeal legislation is passed.

Matthew Fiedler, a health policy fellow at the in Brookings Institution, argued that repealing the mandate alone, without a replacement plan, could have a big impact on prices and that lawmakers just threatening to do so has impacted the market.

“A lot insurers who have been filing for 2018 have already been building in a margin to say, ‘We think there might not be an individual mandate, so we are going to have a sicker pool, so we need to charge much higher premiums,'” Fiedler told ABC News. “In the ‘repeal and delay’ construct you could very well have insurers say, ‘Why am I going to deal with the chaos next year if I don’t even know if there is a business opportunity here in the long run and so I am going to pull up stakes and leave.’”

While the open enrollment period to buy individual insurance on state exchanges does not start until November, insurance companies are far along in their process of designing and submitting preliminary plans and pricing to states. Even if a repeal bill temporarily preserved some part of the law, like the cost-sharing subsides for people purchasing their own insurance for another year or two, experts say repealing the insurance mandates could lead insurance companies to raise prices or leave individual markets immediately.

In January, the Congressional Budget Office published a report analyzing a previous iteration of a repeal-only bill that would have removed the individual mandate immediately and then later eliminated the federal subsidies of individual insurance and the Medicaid expansion two years later. The CBO estimated that within the first year of enactment, 18 million more Americans would become insured because of the mandates repeal. Premiums in the non-group sector would increase by 20 to 25 percent in the first year, according to the report, as compared to projections under current health care legislation.

When cuts to Medicaid and the end of cost-sharing subsidies for individual insurance go into effect, the CBO estimated the number of uninsured Americans would grow by 32 million by 2026.

“If Republicans have been unhappy with the coverage estimates they have been getting so far, I can’t see how a repeal and delay strategy would solve the problem,” Fiedler said.

He went on, “One of the major challenges and one of the reasons Republicans on the Hill moved away from [repeal and delay] six months ago is that upending the whole health care system and then giving insurers no certainty on what would come after is a recipe for disaster. One of the things we have seen is that the insurance industry just does not deal very well with uncertainty … If the last six months have demonstrated nothing else it is that coming to an agreement on health care reform is hard.”