Medicare for all sounded to a substantial number of Americans like a wonderful it, until they learned and thought more about it. Democratic candidates for president noticed the shift. Now, some who backed the proposal initially are altering their rhetoric.

In essence, “Medicare for all” is exactly what the name implies. It would require all Americans to enroll in a government health-care program much like Medicare. Many who liked the idea several months ago were delighted at the idea of “free” government health insurance.

Nothing is ever free, of course. Americans who pay taxes would have to cover the cost of “Medicare for all.”

As more became known about the idea, many people turned against it. They learned “Medicare for all” would permit no private health insurance. And, they thought about shortcomings in the current Medicare program — along with the very real potential for health care rationing if it becomes mandatory and universal.

In April, the nonpartisan Kaiser Family Foundation found through a public opinion poll that about 80% of registered Democrats liked “Medicare for all.” By July, the percentage had dropped to 39.

Two of the leading contenders, Sens. Bernie Sanders, I-Vermont, and Elizabeth Warren, D-Massachusetts, continue to promote “Medicare for all.” Backing away would cost them votes from their hard-core socialist bases, they recognize.

Alone among leading Democratic contenders, former Vice President Joe Biden criticized “Medicare for all” from the beginning. It just wouldn’t work, he pointed out.

Now, several other candidates are hopping on the bandwagon. Sen. Kamala Harris, D-California, is among them. Her health care plan would preserve private insurance.

But in January, Harris said this in a televised interview: “I believe the solution, and I actually feel very strongly about this is, we need to have Medicare for All. That’s just the bottom line.”

Sen. Cory Booker, D-New Jersey, supports “Medicare for all” but, somehow, says he would preserve private insurance.

Weaving and bobbing among Democratic candidates in the presidential campaign boxing ring will continue, as voters learn more about the impracticality of their lavish promises. But, even with changes over “Medicare for all,” one thing remains constant: Each and every one of the top Democrats favors vastly more control over health care by the federal government.

Doing so would mean higher tax bills — for those who pay taxes — and more limits on health care.

That, too, will raise more and more eyebrows among thoughtful Democratic voters. But at some point, candidates such as Harris and Booker will have no more wiggle room left. They will not be able to squirm away from their big-government health-care plan — because, as they say, a leopard cannot change his or her spots.