With midterm elections fast approaching, national polls show Obamacare is still a key issue for Americans.

President Donald Trump promised to dismantle his predecessor's landmark 2010 healthcare law, but to what extent has he succeeded?

• Repealing individual mandate

Congressional Republicans last year finally succeeded in repealing the Obamacare requirement that people buy health insurance or pay a tax penalty.

Mr Trump argued that repealing the mandate would end Obamacare. Nevertheless, the act stumbles on.

The mandate was not as successful as Obamacare's architects hoped in driving younger, healthier Americans into the healthcare marketplace.

Now, as they ditch their coverage, to make up for the loss insurance firms will charge more to the sick or medically vulnerable patients left behind.

In June, the Trump administration allowed insurance companies to offer Americans cheaper, less-comprehensive policies called Association Health Plans (AHPs) that last only up to a year.

Since AHPs are short-term, companies can charge higher premiums or deny coverage based on medical history and pre-existing conditions, which Obamacare made illegal for long-term plans.

These skimpy plans will appeal to young, healthy Americans, , but some AHPs may not cover basics like prescription drugs or maternity care.

Initially, users had 90 days to sign up for insurance on the federal marketplace.

Last year, the Trump administration cut it down to 45 days, and then closed the website every Sunday for 12 hours, citing maintenance.

Funding for the "navigator" programme, under which trained individuals or organisations help people sign up for insurance through Obamacare, has dropped from $62.5m (£48m) to $10m under President Trump.

His administration has also cut Obamacare advertising spending to $10m - a 90% reduction.

• Ending cost-sharing reduction payments

Cost-sharing reduction (CSR) payments from the US government reimbursed insurance companies for covering lower-income Obamacare patients.

When the Trump administration cancelled these payments in October last year, insurance firms increased 2018 premiums to compensate for the loss.

The end of CSR payments had little effect on lower-income Americans, who still receive other healthcare subsidies. But it did lead to a cost hike for patients who pay full-price for their medical coverage.

What's the impact?

For now, former President Barack Obama's signature accomplishment is still standing.

The 2018 government report saw 11.8 million Americans re-enrol in Obamacare plans, and 27% were new users. It's around 400,000 fewer people than 2017 - a smaller figure than expected given the administration's efforts.

Meanwhile, the latest Obamacare insurance premiums will be announced in October - just before the mid-term elections - and they are expected to continue going up.

A Gallup poll earlier this year found 55% of Americans worry "a great deal" about accessing and affording medical care - the fifth year in a row that healthcare has topped the issues list.

Gallup also reported the uninsured rate had dropped to a record low of 10.9% in 2016, but has since risen to 12.3% post-Trump.

What does the existing law do?

The Patient Protection and Affordable Care Act, known as Obamacare or the ACA, was the largest overhaul of the US healthcare system since the 1960s.

It aimed to eventually slow the growth of US healthcare spending, which is the highest in the world.

Obamacare intended to extend health insurance coverage to the estimated 15% of Americans who lacked it and were not covered by other health programmes for the poor and elderly.

The law created state-run marketplaces - with websites akin to online shopping sites - where individuals can compare prices as they shop for coverage.

Some of the more popular provisions include:

• Children can stay on their parent's health care plan until age 26
• No one can be denied insurance for a pre-existing medical condition
• Companies can no longer charge women more than men
• Businesses with more than 50 full-time employees must offer health insurance

Why do conservatives oppose the law?

Republicans say it imposes too many costs on business, with many describing it as a "job killer". However, since the implementation of Obamacare, jobs in the healthcare sector, at least, rose by 9% and a 2017 study found that around 2.6 million jobs could be lost by 2019 if it is repealed.

Conservatives have also decried the act as an unwarranted intrusion into the affairs of private businesses and individuals.

During the Obama presidency, the Republican-controlled House of Representatives took dozens of symbolic votes to repeal the law and forced a partial government shutdown over the issue.

After repeated legal challenges, in 2012 the US Supreme Court declared Obamacare constitutional.

Despite having a majority on Capitol Hill under President Trump, a Republican repeal bid failed in dramatic fashion this year.

Democratic leaders have acknowledged Obamacare is not perfect, and have previously offered to work with Republicans to fix its flaws.

What about 'Medicare for all'?

Growing numbers of left-wing Democrats are coalescing around a universal healthcare plan proposed by former Democratic presidential candidate Bernie Sanders.

He advocates expanding Medicare, the US government's medical coverage programme for pensioners, to all Americans.

Mr Sanders' idea - Medicare for all - would provide healthcare for everyone without fees. It would be funded by higher taxes.

The plan's champions say its tax burden on Americans would be offset by savings for them in an array of medical charges they currently face, such as premiums, co-pays, out-of-pocket expenses and deductibles.

Mr Sanders has cherry-picked a figure from a libertarian study suggesting Medicare for all would save the US $2tn on healthcare spending over a decade.

But the research made clear that estimate was based on hospitals and doctors accepting payments of 40% less for patients who currently have private insurance.

The study found that if current rates stay about the same, US healthcare spending would increase by more than $3tn under Medicare for all.