Obamacare has helped as many as 9.9 million people to get new health insurance, and more than 4 percent of all Americans have gotten health insurance for the first time, according to a new Gallup poll.

It’s the largest poll yet to assess the effects of the 2010 Affordable Care Act, and the findings add to what’s been reported in earlier surveys and the government tally of how many people signed up through the new online exchanges.

The percentage of the U.S. population that has no health insurance has plummeted from an all-time high of 18 percent during the last quarter of 2013 to just 15 percent this past March, says Dan Witters, lead researcher for the Gallup-Healthways Well-Being Index.

“We feel pretty comfortable attributing much of this change to the Affordable Care Act."

About half got insurance on the new state and federal online health exchanges, the survey found, and half got it through Medicaid, an employer or bought it directly from an insurance company.

In total, probably 7.26 million but perhaps as many as 9.9 million people got insurance since the last quarter of 2013, bringing the number of uninsured Americans down from 43.5 million to 36.3 million, Gallup says.

“We feel pretty comfortable attributing much of this change to the Affordable Care Act,” Witters told NBC News.

The survey confirms that people started getting insurance in the last months of 2013 and really started signing up in the first three months of 2014.

The Obama administration says at least 7.5 million people signed up for private health insurance on the online, health insurance exchanges that opened up in October. It says 3 million people have newly enrolled in Medicaid, the federal-state health insurance plan for people with low incomes.

Many of those who got insurance through the exchanges already had insurance. Gallup, which calls and surveys 500 different people, 350 nights a year for a total of 178,000 people annually, says 4.2 percent of Americans got a new healthcare policy using the federal and state exchanges in 2014; 2.1 percent of Americans used the exchanges to get a new policy and did not have a policy in 2013 and 1.9 percent of Americans used the exchanges to get a new policy, but it was a replacement policy for one they already had in 2013.

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Gallup says people who are newly buying insurance tend to rate themselves as a little bit less healthy than the population as a whole, but not by much. About half of all of the adults Gallup surveyed said they were in excellent or very good health, compared to about 37 percent of those who said they were newly insured.

“There is no evidence that the exchanges only signed up extremely sick people,” said Frank Newport, Gallup’s editor in chief.

And there’s a mixed bag agewise. Gallup found younger people aged 18-29 tended to gravitate to buying health insurance directly, not on the exchanges, while those signing up on the new exchanges tended to be in the 50-64 age group. Overall, 30 percent of those getting insurance for 2014 were 18 to 29; 24 percent bought insurance on the exchanges and 37 percent got it elsewhere.

That fits in with some of the first data from the beginning of the sign-up period last year, which suggested middle-aged people were piling on to the exchanges.

“The newly insured outside the exchange actually skew younger,” Newport said.

Experts say it doesn’t really matter what mechanism people use to buy insurance, but the balance of older and sicker people to younger and healthier will affect whether an insurance company finds it feasible or profitable to continue offering policies, and it can affect future premiums.

Some experts have suggested that an ideal pool of insurance customers would have 40 percent of customers in the 18 to 34 age group.

“Politics is by far the huge driver of your opinion of the Affordable Care Act."

One group hasn't benefited quite as much yet — Hispanics. Newport says the percentage of Hispanics nationwide without health insurance has fallen from 40 percent to 37 percent.

Gallup also asked people about their attitudes to Obamacare and found deep, unshifting divides. More than half of those surveyed this month, 54 percent, said they disapprove of the Affordable Care Act while 43 percent said they approved of it.

“Politics is by far the huge driver of your opinion of the Affordable Care Act,” Newport said. “These attitudes are so rooted in partisanship that it is going to be very difficult to change it.”

One small shift — more people said they believed Obamacare would not change their own personal health care, a slight shift away from a majority who had said it would make things worse. Forty-five percent said Obamacare would make health care worse in the U.S, down from 48 percent in March; 37 percent said it would make health care better and 15 percent said it would make no difference.

“We are moving Republicans out of the box where they are saying it is going to hurt health care,” Newport said.

Attitudes also seem to affect who is benefiting from the law. In 20 states that both embraced Obamacare by setting up their own exchanges and by expanding Medicaid to more people, the uninsured rate fell from 16.1 percent to 13.6 percent.

In states that rejected Medicaid expansion and that let the federal government run their exchanges, the rate of uninsured barely moved — from 18.7 percent to 17.9 percent.

"The states that have embraced it have dropped at a rate that is three times faster than the ones that haven't," Witter said.