Three times on "Meet the Press" last Sunday, House Minority Leader Nancy Pelosi said the payment individuals must eventually make for failing to buy insurance under the health-care law is a penalty, not a tax.

"It's a penalty that comes under the tax code," Pelosi said, "for the 1%, perhaps, of the population who may decide that they're going to be free riders" by not buying insurance.

Moderator David Gregory persisted. "But it's a new tax. It is a new tax on the American people," he said.

"No, no, no, no," Pelosi responded. "It's not a tax. It's a penalty for free riders."

So what is the payment that virtually all citizens must make if they decline to obtain health insurance when that provision of the Affordable Care Act takes effect in 2014?

In his Supreme Court opinion declaring the law constitutional under Congress's taxing authority, Chief Justice John Roberts called it a tax no fewer than 26 times. The health-care law itself repeatedly refers to the payment as a penalty, but Roberts said that didn't matter. The conclusion about what it is, he said, "should not change simply because Congress used the word 'penalty.'" 

For him, the issue is how it actually works, not the label attached to it in the statute.

Penalties, Roberts said, work much differently from taxes. Quoting an earlier Supreme Court decision, he said a penalty "is an exaction imposed by statute for an unlawful act." But failing to buy health insurance is not unlawful, because a citizen has an alternative -- either buy insurance or pay a tax. The conclusion: It cannot be a penalty.

"Neither the Act nor any other law attaches negative consequences to not buying health insurance, beyond requiring a payment to the IRS," Roberts wrote. "The shared responsibility payment merely imposes a tax citizens may lawfully choose to pay in lieu of buying health insurance."

It is, he put it succinctly, “a tax on going without health insurance.”

Is all this semantics, or does it matter? It made all the difference to Chief Justice Roberts. His opinion makes it amply clear that if he thought it wasn't a tax, he would not have voted to find it constitutional. Under the law of the case, the Supreme Court declared that payment a tax, not a penalty.

The relationship between Barack Obama and John Roberts got off to a rocky start, but Thursday brought the president and the chief justice together in a historic alignment of a conservative judge and a progressive president.

Veteran Supreme Court lawyer Tom Goldstein told NBC’s Pete Williams that “the Affordable Care Act was saved by Chief Justice John Roberts” – due to his decisive fifth vote and his majority opinion upholding the 2010 health care law as an exercise of Congress’s power to tax.

Tim Sloan / AFP - Getty Images

US Supreme Court Chief Justice John G. Roberts participates in the court's official photo session on Oct. 8, 2010 at the Supreme Court in Washington, DC.

Obama voted against confirming Roberts as chief justice in 2005, arguing that he lacked a heart and had “far more often used his formidable skills on behalf of the strong in opposition to the weak." Roberts, Obama said then, “seemed consistently to side with those who were dismissive of efforts to eradicate the remnants of racial discrimination in our political process."

It was no surprise when Obama said as he campaigned for president in 2008 that he wouldn’t have appointed Roberts to the high court -- but after Thursday’s decision by Roberts, Obama has good reason to be grateful to his predecessor, George W. Bush, for having done so.

Roberts inadvertently got Obama’s presidency off to an awkward start on inauguration day when the chief justice flubbed the words of the oath of office as he tried to administer it to Obama, putting the word “faithfully" in the wrong place. That embarrassment led to a do-over the next day at the White House.

The two men have a few superficial similarities – they’re both ambitious Midwesterners, both Harvard Law School graduates, and both are ‘no drama’ un-flamboyant types – but after law school each pursued divergent career paths and adopted clashing ideologies.

Roberts started out as a Reagan Republican, clerking for the man Ronald Reagan later elevated to chief justice, William Rehnquist, and working in the White House counsel’s office under Reagan and in the Reagan Justice Department.

Roberts maintains some attachment to the Reagan Era: for his very first speech as chief justice he chose to accept Nancy Reagan’s invitation to speak at the Reagan library in Simi Valley, Calif.

As chief justice, Roberts has so far established an undeniably conservative record, for example, he joined the five-to-four decision that Obama has most vehemently criticized: the Citizens United ruling that allows independent political spending by corporations and labor unions.

Right after the court handed down that decision, Obama took the occasion of his State of the Union address to scold the justices – some of whom, including Roberts, were sitting right in front of him in the House chamber.

Justice Samuel Alito caused a furor that night by shaking his head in disagreement at the way Obama described Citizens United. After the president said it would “open the floodgates to special interests – including foreign corporations” to influence elections, Alito seemed to mouth the words, “not true.”

Roberts was dismayed by that dramatic nationally televised collision of the executive and judicial branches, telling an audience at the University of Alabama that while he didn’t object to public officials voicing criticism of the decisions of the Court, "to the extent the State of the Union has degenerated into a political pep rally, I'm not sure why we're there.”

He said it was “very troubling “ to have members of Congress (Democrats, who hated the Citizens United decision) "literally surrounding the Supreme Court, cheering and hollering while the court -- according to the requirements of protocol -- has to sit there expressionless….” (Although Roberts did attend State of the Union addresses in 2011 and 2012.)

That comment illustrates why Roberts is far more comfortable in the hushed and stately environment of the building across the street from Capitol – no “cheering and hollering” are ever heard inside the courtroom and no pep rallies are allowed.

At age 57, Roberts seems likely to serve many more years on the high court. It’s anyone’s guess as to whether his decision in the Affordable Care Act case will be the one that, a quarter century from now, legal analysts see as his most enduring. Too many unknowns lurk out in the future and too many future acts of Congress remain to be decided by Roberts and his colleagues.

Despite Thursday’s decision, his record so far has been not that of an Obama progressive, but of a conservative.

For example, he wrote the majority opinion in a 2007 case that told public schools which had no history of racial segregation they couldn’t use a student’s race as a basis for assigning him or her to a school, even if the larger goal was to achieve greater racial diversity in the school population.

“The way to stop discrimination on the basis of race is to stop discriminating on the basis of race,” Roberts wrote.

And Roberts in 2009 wrote the majority decision in a Voting Rights Act case that cast deep doubt on whether section 5 of that law will survive. Writing for the court, Roberts questioned “whether conditions continue to justify such legislation.”

Neal Katyal, who served as acting solicitor general in the Obama administration, and defended the Affordable Care Act in the appeals court, said Roberts’s decision on the ACA was quite characteristic of him.

 “This is – to a T— the Voting Right Act opinion in 2009 which had all the similarities (to Thursday’s),” Katyal said. “You had an oral argument in which he and other members of the court were extremely questioning…. You had pundits who said that it was going to be declared unconstitutional after the oral argument.”

Then when the decision was announced, “the chief spent several minutes explaining why the act was an unprecedented intrusion into federalism, and then you have the chief reversing course, minutes into his hand-down, and saying “but it’s constitutional because the court rewrites the statute, essentially, to save it from a constitutional problem. All of those are the same exact moves that happened here,” Katyal said.

Roberts told the Senate Judiciary Committee during his confirmation hearings that "judges are not politicians who can promise to do certain things in exchange for votes” and he reminded Americans again in his Thursday that if they see problems created by the ACA, then it’s up to them on Election Day, and not up to the court, to fix them.

Policy choices are “entrusted to our Nation’s elected leaders, who can be thrown out of office if the people disagree with them. It is not our job to protect the people from the consequences of their political choices.”