Republicans jumped on the court’s ruling that the healthcare law's individual mandate, which the Obama administration originally pitched as a penalty or fee for those who don’t purchase insurance, is constitutional under Congress’s power to tax, calling it evidence that President Obama has raised taxes on the middle class.

But the distinction highlights the difficulty the Romney campaign has in going after Obama over the healthcare law. As governor of Massachusetts, GOP presidential candidate Mitt Romney instituted healthcare reforms that included an individual mandate. At the time, he portrayed it as a penalty or a fine, rather than a tax.

On Monday, Democrats seized on comments Romney spokesman Eric Fehrnstrom made to MSNBC, saying the former governor agrees with Obama that the individual mandate upheld by the Supreme Court last week is a penalty or a fine and not a tax.

But this was a shift from comments Romney made last week in response to the court’s ruling.

“ObamaCare raises taxes on the American people by $500 billion,” he said during a press conference across the street from the U.S. Capitol.

Voters were split on the Supreme Court’s ruling overall, with 50 percent saying they agree that the healthcare law is constitutional versus 49 saying they disagree.

The law has gained in popularity in recent months, with 51 percent saying they favor most or all of the provisions against 47 that oppose all or most of it. In January, those numbers were reversed, with 50 percent opposing most or all and 45 in favor.

Still, a majority, 51 percent, said they favor repealing the law in its entirety, compared to 47 percent that want it kept in place.

The individual mandate is opposed by 51 percent and favored by 48.