Is it a tax or a penalty? Obama and Romney struggle to define aspect of healthcare law.

It looks like a tax, smells like a tax, and the Supreme Court says it must be a tax. But politicians in both parties are squirming over how to define the Thing in President Barack Obama's health care law that requires people to pay up if they don't get health insurance.

The problem for Obama is that, if the Thing is indeed a tax, he is by definition a raiser of taxes on the middle class, which he promised not to be.

If that sounds like an opportunity for Republican presidential rival Mitt Romney, well, it's not that simple.

Obama's health care law is closely modeled on the universal-coverage plan Romney achieved as Massachusetts governor. That plan contains a penalty for noncompliance similar to the one in the federal law upheld by the court last week.

So if Obama is a raiser of taxes, so is Romney.

Contortions have ensued over what to call this health care Thing.

Romney adviser Eric Fehrnstrom strayed from Republican talking points when he told MSNBC that Romney agrees with Justice Antonin Scalia's minority opinion that "very clearly stated that the mandate was not a tax."

That position is at odds with congressional Republicans who are determined to portray the Thing as an Obamatax pure and simple.

"The American people do not want to go down this path," House Speaker John Boehner, R-Ohio, said. "They do not want the government telling them what kind of insurance policy they have to buy, and how much they have to pay for it, and if you don't like it we're going to tax you."

As for the other side, House Democratic leader Nancy Pelosi of California and some others have taken to calling it a "penalty for free riders."

"This is a penalty on free riders," echoed Sen. Chuck Schumer, D-N.Y.

Just as everyone loves motherhood and apple pie, no one loves a free rider. Not Democrats. And not Republicans.

But Democrats didn't make that up.

Some years back, Romney called his own Thing a penalty on "free riders."

The whatever-it-is starts in 2014, will be collected by the Internal Revenue Service and functions like a tax in that its amount is keyed to the income of those who must pay it.

The Obama administration always shied away from calling it a tax for the obvious reason that tax increases are political trouble. But, paradoxically, his health care law only stands today because the high court considered the insurance mandate part of Congress' broad powers of taxation, therefore constitutional.

The court carefully parsed all of this in a migraine-inducing summary of Chief Justice John Roberts' written decision.

"The Affordable Care Act describes the 'shared responsibility payment' as a 'penalty,' not a 'tax,'" it says. "That label is fatal to the application of the Anti-Injunction Act. It does not, however, control whether an exaction is within Congress' power to tax. In answering that constitutional question, this Court follows a functional approach, 'disregarding the designation of the exaction, and viewing its substance and application.'"

In other words, the Thing is a tax.