Senate Majority Leader Mitch McConnell is delaying the vote on the Senate health care bill -- originally slated to take place before the July 4 holiday -- while a number of GOP senators remain opposed to their own party's unpopular proposal.

The House passed its version of health care reform in May, but only narrowly, and with no Democratic support. Republicans have championed repealing and replacing the Affordable Care Act (ACA) or Obamacare since its passage in 2010, but as the months of President Trump's administration drag on, some in Washington, D.C., are becoming skeptical that they can make good on that Trump campaign promise. So, what happens if -- well, nothing happens?

If Congress doesn't pass a new health care bill, how does that affect health care?

Obamacare will remain the law of the land, although it will be in shaky shape. Gerald Kominski, director of the UCLA Center for Health Policy Research, says that efforts to repeal the bill have created an atmosphere of instability that have exacerbated the ACA's problems.

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"Of course [the ACA] is imploding," Kominski tells CBS News. "[President Trump] is pushing it off a cliff."

That means insurers will continue to leave the health care markets set up by the ACA, particularly in areas with a high "risk profile" that have more people with chronic illnesses and other things that could increase health care costs. Insurers, Kominski says, are "the opposite of first responders. They're the last responders. First responders run to the danger. Health insurers run away from the dangers."

Experts on both the left and right agree that the new atmosphere of uncertainty about the ACA that would result from a failure to pass a new bill would cause problems.

"If they don't [pass legislation] then you're going to take everything that was already wrong with the ACA and add more uncertainty on top of it," says Robert Graboyes, a senior research fellow and health care scholar at George Mason University's Mercatus Center.

Does that mean higher premiums?

Broadly speaking, the answer is probably yes, as premiums have already gone up considerably over the last year. But a lot of that depends on what the Trump administration decides to do next, particularly when it comes to funding the law.

Premium subsidies, which the government gives out to help people pay for health insurance plans based on their income and what kind of plan they want, would stay untouched. However, the Trump administration could cut off cost-sharing reduction payments, or CSRs, which are paid to insurers to help defray the costs of deductibles and the like.

"We've seen insurers pull out in the face of the uncertainty created by the administration and we've also seen insurers propose significant premium increases, due to that uncertainty," says Larry Levitt, a senior vice president at the Kaiser Family Foundation. So I think if the Senate bill fails, I think there's just tremendous uncertainty about what the Trump administration will do in running the marketplaces for 2018, and we could certainly see more insurers pull out or raise premiums significantly in the face of that."

How big could the premium hikes get?

If the Trump administration gets rid of CSRs, they could go quite high. In North Carolina, Blue Cross Blue Shield is already warning its ACA enrollees that premium prices could increase more than 20 percent if the cost-sharing premiums are done away with. Covered California, the state Obamacare exchange, has asked insurers to provide two sets of premium rates -- one with CSRs, and one without them. If the CSRs stick around, which is up to the administration, and the federal government keeps funneling money to insurance companies, the premium rate hike is expected to be around nine percent.

What about penalties for being uninsured?

Without any new legislation, Obamacare remains the law of the land. That includes the financial penalties on those who don't have insurance. But the Trump administration could -- and has already indicated it might -- simply choose not to enforce those penalties. The penalty was already difficult to enforce under Obamacare, Graboyes said. But any emphasis that the penalty won't be enforced could encourage young and healthy people who might have purchased health care to stay out of the market, potentially hiking premiums for others.

Would that mean that the ACA would just collapse on its own and go away?

No. Again, the law stays on the books unless Congress gets rid of it and replaces it with something else. "Reversion to the pre-Obamacare status quo is not possible without federal legislation," says Michael Cannon, the director of health policy at the libertarian Cato Institute.

"The Medicaid expansions and subsidies will still be on the books, as will the insurance regulations," says conservative health care analyst Avik Roy. "Businesses can 'collapse onto themselves' and go away. When government programs fail, they stay on the books."

At the same time, insurance companies would be likely to keep pulling out of individual counties, meaning that more and more Americans would have no ACA options whatsoever, or perhaps just one plan to choose from. According to Kaiser Family Foundation, 47 counties -- encompassing 33,894 enrollees -- are at risk of having no insurer on the marketplace for them in 2018.

What would a failure to pass legislation mean for Medicaid?

"If the House and Senate can't move forward with this disastrous legislation that they're proposing, then for the time being Medicaid continues as is," says Kominski.

What are the chances the bill passes?

Senate Majority Leader Mitch McConnell, R-Kentucky, is considered an extremely able legislative tactician. However, he's in an uncomfortable spot. Some conservative Republican senators oppose the bill because they believe it doesn't go far enough in repealing the ACA, while more moderate members of the GOP caucus worry the bill will hobble popular services. Democrats, meanwhile, are uniformly opposed to the legislation.

Republicans have a narrow majority in the Senate, controlling 52 seats to the Democrats' 48. That means McConnell can afford two no-votes from Republicans, while three would kill the bill. Nine Republicans now oppose the bill in its current form, meaning it will be exceptionally difficult to pass this legislation by the end of July.