Will they or won’t they? Insurers offering health coverage on state exchanges are in the process of deciding whether they’ll continue to offer insurance — and if so, at what price — next year under the Affordable Care Act.

Related: Insurers riding wave of chaos in ACA planning coverage

But considering all the uncertainty surrounding not just cost of coverage, but the ACA itself, some places could end up with no insurer options at all, if companies decide to back out of continuing in the program.

A report from The Hill says that five places in the country are in particular danger of ending up with zero insurer choices. One reason is that insurers only have to decide how much to increase premiums to cover costs that have been higher than expected, given that people have flocked to buy coverage on the exchanges and as a result companies have seen higher claims than they expected.

Another is the game the government is playing around the cost-sharing reduction (CSR) payments insurers were promised, but that the Trump administration has threatened to withhold.

According to a PBS report, those payments to insurance companies were intended to cover out-of-pocket costs and deductibles for low-income consumers, but a court ruling found that those payments were not constitutional unless Congress authorized them.

And since the Republican Congress’s avowed purpose has been to repeal and replace the ACA, replacing it with its own version of health care coverage —a n effort that thus far has been unsuccessful — the CSR payments that have not been made are in limbo.

And considering that 7 million people — more than half of those on the exchanges — qualify for those subsidies, that’s a big chunk of change that insurers haven’t yet seen. They’re not prepared to forego even more, especially if the Trump administration decides not to pay up. And neither Congress nor Trump have said definitely that the money will come.

Related: Brokers giving up on ACA

Even more uncertainty that could drive insurers out of the exchanges includes a lack of enforcement of the individual mandate — something that’s already a possibility, since the IRS said back in February that in view of Trump’s executive order to loosen up on enforcement of ACA rules, it would not reject tax forms from people who fail to specify whether they have health insurance.

And then there’s the cost of plans, which would drive customers from the market — especially without those already-in-doubt subsidies: a Kaiser analysis indicates that premiums could rise by an average of 19 percent across the board if the CSRs fall by the wayside.

Then too, of course, it’s not yet a sure thing that the ACA itself will survive, although the outcry over the House’s attempt at replacement has Republican senators scrambling to write their own version of the American Health Care Act.

But in the meantime, an awful lot of people could be left hanging if insurers decide that so much uncertainty isn’t an acceptable condition of continuing to do business on the exchanges.

There have been a couple of suggestions from senators on ways around the problem; Sen. Lamar Alexander, R-TN, who is also the chairman of the Senate Health, Education, Labor and Pensions Committee, has gotten together with Bob Corker, Tennessee’s other senator, to propose a bill allowing residents in places with no insurers to use their ACA financial assistance to buy any state-approved plan.

On the Democratic side, Sen. Claire McCaskill, D-MO, suggests instead that those in counties without insurers could buy their coverage on the Washington, D.C. exchange, used by many lawmakers and congressional staff.

Here are the five places in the country that are most at risk for losing coverage altogether, thanks to a lack of willing insurers.

5. Missouri

At present, 25 counties have no willing insurers for 2018, since Blue Cross Blue Shield of Kansas City’s announcement last month that it was exiting the marketplaces.

While it’s not definite at the moment — insurers have till fall to make a firm commitment — right now that’s how things stand. State officials are probably working to entice other insurers to step in — which is what Arizona had to do last year for Pinal County, convincing Blue Cross Blue Shield of Arizona to provide coverage for county residents.

Related: Anthem likely to retreat from Obamacare for 2018, analysts say

In Tennessee, Knoxville was saved by Blue Cross Blue Shield of Tennessee, although in covering the area for 2018, the company is adding “a few caveats.”

“I think the Blues are, generally speaking, more committed to staying in the individual market,” Cynthia Cox, associate director for the Program for the Study of Health Reform and Private Insurance at the Kaiser Family Foundation, is quoted saying in the report.

Cox adds, “That’s what makes the Missouri situation more troubling than some of the other places where we’ve been looking, is that without the Blue Cross Blue Shield plan, it’s not clear who’s going to move into those counties.”

4. Iowa

For most Iowa counties, Medica is the sole choice for coverage — and the company hasn’t yet decided whether it’s going to stick it out for another year. And in five counties, Gundersen Health Plan is the go-to source — it too has not yet decided whether to hang in there.

April saw both Aetna and Wellmark Blue Cross and Blue Shield bow out of Iowa’s exchange.

And Wellmark, for its part, has a list of conditions it says are needed for it to reenter the exchange for another year. According to an op-ed by its chairman and CEO, John Forsyth, it wants continuous coverage incentivized, as well as tighter rules for special enrollment periods, financial help based on age and income, reinsurance being offered and flexible plan design allowed.

Related: Aetna quits Iowa ACA market, is second insurer to leave

3. Nebraska

Think Iowa and you’re pretty close to the situation in Nebraska.

With Aetna departing the exchanges last month, Medica was left as the only insurer selling on the state’s exchanges.

Geoff Barsh, vice president for individual and family business at Medica, is quoted saying, “Things are still changing daily. We’re still looking at changes and will continue to evaluate things. We are still planning to participate in the Nebraska market for 2018. We haven’t made any final decisions on that yet.”

Related: Aetna loses on merger, plans more ACA pullbacks

2. Knoxville area, Tennessee

When Humana announced it was departing the exchanges back in February, that left Knoxville high and dry for 2018. There were two insurers left in the state, so Julie Mix McPeak, Tennessee’s insurance commissioner, tried to get at least one to expand coverage.

Related: Trump points to Humana exit from ACA as sign of failure

And while Blue Cross Blue Shield of Tennessee agreed, it set conditions on its presence: that it could bail on the Knoxville market “in the event of any post-bid changes that destabilize the market.”

1. Rural areas

With fewer people, there’s less demand for coverage in rural areas throughout the country, and they’re finding it tough to keep insurers interested with such small pools of customers.

The report says that on average, urban areas had 2.5 insurers participating in 2017, compared to two insurers in more rural regions.

And a fair number of rural areas have only one insurer anyway — so if a company leaves that state, it “could mean there is no coverage option for some people living in those counties. In those counties with only one issuer, the future of the exchange essentially depends on that one company,” Cox says in the report.

She adds, “I think just within a given state the rural areas are probably most at risk of having no insurance company. It’s easier for a plan to set up a favorable network in an urban area, and there’s also generally just more insurers wanting to participate in urban areas.”