(Bloomberg Gadfly) -- If at first you don't succeed, threaten toblow up the health-care system and try again.

On Friday morning, President Donald Trump tweeted that if theSenate fails to pass its proposed bill to replace the AffordableCare Act (ACA), then it should just repeal the ACA and figure out areplacement later.

The tweet seemed to reverse the president's previously heldposition that repeal and replacement should happensimultaneously.

Related: 5 weird Senate health care billeffects

And it created a big potential mess for health-insurancemarkets.

One of the few perceived benefits ofthe fundamentally harmful Senate bill passing was that itwould, at the very least, resolve the uncertainty that has plaguedhospitals and ACA-exposed insurers all year.

The president's new strategy -- and its reminder of hisinconstancy -- ratchets policy uncertainty up once again.

This could just be a bluff, a strategy to strong-arm theSenate into passing a replacement. The repeal could (and likelywould) be paired with a one or multi-year delay, giving the GOPmore time to work on a replacement.

But repeal-then-replace is only rearing its head again becauseSenate Majority leader Mitch McConnell doesn't seem to be gettingthe Senate close to a passable bill as it heads into a July Fourthrecess. Moderate Republicans want to make the bill more like theACA, while conservatives want to gut protections for those withpre-existing conditions, and there's little middleground.

Related: Poll shows little support ofBCRA

Those issues may mean the Senate bill may fail or take a verylong time to pass, increasing pressure to follow with thepresident's repeal idea. The issues dividing Republicans won't goaway, meaning there's a real possibility a replacement will nevercome. That's a potentially disastrous prospect for hospitals andinsurers.

Because of the rules of the budget-reconciliation process thatlets the GOP pass a bill with only 50 Senate votes, a straight ACArepeal won't get rid of its regulations, including those thatprevent insurers from denying coverage, require insurance meet someminimum standards and protect people with pre-existingconditions.

The problem is that, without ACA subsidies to help people buyinsurance and its mandate pushing healthy people to sign up, thoseregulations don't work; enrollment is too low and costs are toohigh.

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Sicker people would be more likely to buy insurance than healthyones. Insurers would flee the ACA exchanges in droves. Insurancepremiums and the number of people without insurance coverage wouldbe much higher than even under the House's American Health Care Act(AHCA) or the Senate's Better Care Reconciliation Act (BCRA),according to a Congressional Budget Office estimate.

Under a straight repeal, 18 million people would losecoverage in the first year after the repeal, jumping to 27million in the first year the ACA's Medicaid expansion is ended,which could vary, depending on how a repeal bill isstructured.

This sort of repeal would deal a big blow to insurers such asCentene Corp., Anthem Inc., and Molina Healthcare Inc., which havea large presence on the individual exchanges.

They actually benefit from the fact that the Senate bill keepsbig chunks of the ACA around for a while. It would also hurtothers, such as UnitedHealth Group Inc. and WellCare Health PlansInc., which have bet big on Medicaid.

Hospitals, many of which are already in bad shape due to costpressures and high debt loads, would suffer the most. Rapidcoverage losses would mean a potentially dramatic drop in revenue,and a large increase in the amount of uncompensated care.

Senator Ben Sasse has suggested cancelling August'scongressional recess and holding hearings six days a week in orderto figure out a replacement in a repeal-first scenario, in order toavoid these worst-case outcomes. But there's no guarantee thisticking time bomb will be defused.

And repealing in this way ensures health-care chaos will likelyget worse even before a repeal takes effect. Insurers have beenpulling out of the ACA's exchanges already due to policyuncertainty, and there's even less incentive to stick around if thewhole thing might be destroyed.

The Senate may ignore Trump's Twitter musings and continue tohammer out a compromise. But no matter what, one tweet has expandedthe range of possible outcomes for the health-care sector in a veryscary way.

This column does not necessarily reflect the opinion ofBloomberg LP and its owners.

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