It is generally assumed that the biggest obstacle to a national health plan like Medicare for All will be the large tax increase needed to pay for it. But new polling shows another challenge: Almost half of the American people don't know that they would have to change their current health insurance arrangements if there was a single-payer plan.

Expand chart Data: Kaiser Family Foundation Health Tracking Poll conducted Oct. 5-10, 2017; Chart: Chris Canipe / Axios

Why it matters: Current insurance plans leave a lot to be desired for many people, and it is entirely possible that some people would want to switch to a Medicare for All style plan. But the public has resisted being forced to change their health care in the past — don't forget the uproar over the cancelled plans at the launch of the Affordable Care Act.

So requiring people to change could trigger blowback and would certainly provide a talking point to help opponents scare people about single payer.

The details: Overall, the general idea of a national health plan is pretty popular, with 53% of the American people favoring a national health plan — 30% strongly favoring it and 23% somewhat favoring it. On the other side, 31% strongly oppose it and 13% somewhat oppose it. Democrats and Republicans split on the idea, as expected.

But as the chart shows, somehow, 47% of the American people think they would be able to keep their current health insurance — even though a single payer Medicare for All style plan would do away with employer-based insurance.

52% of Democrats, the group most supportive of single payer as an idea, think they will be able to keep their plan.

Notably, 44% of people with employer-based insurance think they would be able to keep their current plan.

Advocates of single payer consider it a virtue that employer-based health insurance would be eliminated. Health reformers on the right would also do away with employer-based insurance, but they would replace it with tax credits for private insurance, not a government plan.

There are also more targeted public insurance proposals for people who can't get Medicaid or marketplace coverage — including a government-run public option, a Medicare buy-in for 50-64 year olds, or a Medicaid buy-in option on the ACA marketplaces. They wouldn't threaten people's current health care arrangements, but they are far from the rallying cry for some progressives Medicare for All may be, and they're no slam dunks in the current political environment.

The bottom line: There is no sweeping health reform plan without tradeoffs, as we learned with both the ACA and the Republican repeal-and-replace plans. The fact that so many people don't know that a national health plan would require them to change their insurance arrangements underscores the challenge of making the transition from a popular idea to a reality for a single-payer national health plan.