One of the biggest health-care issues in this election season is pre-existing conditions. It features prominently in key races, including that of New Jersey's U.S. Rep. Tom MacArthur, who is fighting a challenge by Democrat Andy Kim. Kim says he got into the race mostly because of MacArthur's  effort that could have changed the federal law on pre-existing conditions.

But it's a term that may sound technical, even wonky. So I'll break it down.

Let's imagine for a moment that I need a Rolls Royce Phantom. I desperately need that Rolls Royce to live the life of my dreams. I need a Rolls to bring joy to my family and do the things I always wanted to do. It will complete me. In our free society, the law absolutely guarantees my right to buy that car — or any car.

But just any car won't do for me what I need it to do. It has to be the Phantom. The problem is, I don't have $417,000 (plus tax) to buy the car — unless I sell my house. Poor me.

Now, instead of a Rolls Royce, what I really need is a new heart, because I was born with a congenital defect and the heart I have is failing. The health insurance companies know this, so they don't want to sell me an individual policy, knowing I will cost them a lot of money.

The law could require the company to sell me a policy that covers my pre-existing condition, but lets them charge what they want. Of course, they will charge me more to cover my higher risk.

This was how it worked in some states before the Affordable Care Act — Obamacare — and the results were astronomical premiums that only the very rich could afford, like Rolls Royces. Other states allowed the insurers to simply refuse to sell any policy, at any price, to a high-risk person.

Obamacare changed that for people under 65 who were not poor enough to qualify for Medicaid or lucky enough to have access to an employer group plan. Obamacare says insurance companies can't refuse to cover people with pre-existing conditions or charge them any more. Everyone can buy the same coverage at the same price.

Any politician or pundit who supports — or supported — a proposal that lets insurance companies treat people with preexisting medical conditions (as many as 129 million Americans under 65 years) differently from perfectly healthy people is selling you a dream you may not be able to afford.

Drew Harris, D.P.M., is a member of the Inquirer's Health Advisory Panel, a health-care consultant, an assistant professor at the Thomas Jefferson University College of Population Health, and director of the scholarly inquiry and health policy program at the Sidney Kimmel Medical College