As happy as President Barack Obama was Thursday, he might have harbored a little bit of regret knowing that he voted against John Roberts' nomination to the Supreme Court.

Now chief justice, Roberts was the deciding factor in a 5-4 ruling that determined Obama's Affordable Care Act is indeed constitutional. Appointed in 2005 by President George W. Bush, Roberts broke from his fellow Republican-appointed justices and shocked the nation to the point that CNN and FOX News actually got the story wrong at first.

Since his service in the Reagan and first Bush administrations and appointment to the federal appellate bench by the younger Bush in 2003, Roberts has been considered a reliable voice for conservatives. That's partly why it was such a shock for Republicans when Thursday morning he declared that Obama's health reform law  embodies sound policies. That judgment is entrusted to the nation's elected leaders.

This was the second time within a week the chief justice sided with his liberal colleagues on the Supreme Court. On Monday he voted to nullify parts of the anti-immigrant law in Arizona.

Roberts does have a substantially conservative record overall. He worked in the Reagan administration as a lawyer where one of his main duties was to write legal documents presenting the president's position on abortion, the hottest of all hot topics. Roberts also signed a legal document that encouraged the court to consider overturning Roe vs. Wade.

In 2007, Roberts voted in Gonzales vs. Carhart to uphold the constitutionality of Bush's Partial-Birth Abortion Ban Act. He also made a ruling that declared depictions of animal cruelty an unconstitutional addition to freedom of speech.

In Parents Involved in Community Schools vs. Seattle School District No. 1, Roberts helped the court decide that race could not be one of the main factors used to determine which school district a student attends. He cited Brown vs. Board of Education and wrote, the way to stop discrimination on the basis of race is to stop discriminating on the basis of race.

Roberts has not always made decisions that could be labeled right-wing. With their lifetime tenure, Supreme Court justices are in the enviable position of not having to pander to any constituents. Outlawing so-called partial-birth abortion, for example, has broad support. 

Roberts has been tagged as a conservative-leaning judge in part because of the president who appointed him, even if his record doesn't completely back it up. Roberts has generally made conservative decisions, but not always.

During his Supreme Court confirmation hearings Roberts decribed his role as umpire and said, It's my job to call balls and strikes, and not to pitch or bat.

After his surprising approval of the individual mandate as a tax, many pundits have asked why Roberts made such an out-of-character decision. Maybe he didn't.