WASHINGTON — Victory at the Supreme Court for President Barack Obama and Democrats on health care is reopening political divisions within the party over the unpopular law.

Four months to an election with control of Congress in the balance, the court’s affirmation of the law left several Democrats insisting that the issue was settled and it’s time to focus on helping the sluggish economy.

Other Democrats saw the newfound attention as a chance to reset the debate and make a fresh case for the law’s more popular elements, especially as 12.8 million people start getting health insurance rebate checks in the coming months.

The most vulnerable Democratic incumbents and challengers — Montana Sen. Jon Tester and North Dakota’s Heidi Heitkamp among them — cautiously welcomed the court’s judgment but said the law could be improved.

Even before Obama signed the measure in March 2010, Republicans were unified in opposition and clear in their message: repeal and replace. The White House and divided Democrats have been frustrated in trying to explain and sell the law to a skeptical public in a sharp contrast to the GOP. The court’s decision was a reminder of political reality.

Two years ago, grassroots outrage over health care contributed to the Democrats losing the House majority and seven Senate seats. Republicans and outside groups promise more of the same in the campaign push to November.  

The court has “done a favor” for Republicans, freshman Rep. Allen West of Florida, who owes his seat in part to that anger, said in an interview. “Why would the Obama administration and Democrats want the pre-eminent issue of 2010 to be the pre-eminent issue of 2012?”

Conservative leader Richard Viguerie said the court’s decision has raised that anger to “a revolutionary fervor that will sweep President Obama and many other Democrats from office.” The Tea Party Express appealed to its supporters for money and backing to defeat Obama and “a liberal U.S. Senate that have foisted ‘Obamacare’ down our throats.” Outside groups, both parties and candidates have been furiously fundraising off the ruling.

In North Dakota, Crossroads GPS released an ad Friday that calls out Heitkamp, the Democratic Senate candidate, for her support of the law and contends that it raises taxes and expands regulations. Crossroads GPS is the conservative-leaning group tied to former President George W. Bush’s longtime political director, Karl Rove.

Looking to finesse a difficult issue, Heitkamp has aired an ad that argues for the law in personal terms.

“I’m Heidi Heitkamp and 12 years ago, I beat breast cancer,” she says. “When you live through that, political attack ads seem silly.”

The former state attorney general, who’s in a close race with Republican Rep. Rick Berg, said the bill has its good and bad points and needs to be fixed but that she would never deny coverage to seniors.  

In suburban Chicago, Democratic candidate Tammy Duckworth said that as a survivor of a health crisis, she understands the importance of affordable health care. Duckworth, who piloted a Black Hawk helicopter in Iraq, lost both legs when her aircraft was hit in 2004.

She highlighted the popular elements of the law: banning denial of coverage for people with medical conditions, allowing children to stay on their parents’ insurance until age 26, and reducing seniors’ Medicare prescription drug costs by closing the “donut hole.” But Duckworth complained about the law’s “unfair burden on employers, especially our small businesses,” and promised to address the issue if she ousts first-term Republican Rep. Joe Walsh.      

Public opposition to the health care law remains high. Forty-seven percent of respondents in a recent Associated Press-GfK poll said they oppose the law while 33 percent said they support it. Thirteen percent said they are neutral. Those who strongly oppose the legislation also outnumber those who strongly support it, 32 percent to 17 percent, about a 2-to-1 margin.

Critical to both parties, just 21 percent of independents support it, the lowest level of support the AP-GfK poll has recorded on the issue.

Much of the polling does find strong support for individual elements, like allowing young adults to remain on their parents’ plan to age 26. Some Democrats see that as an opening to reframe the debate.

“I see this as a huge moment for us,” Sen. Barbara Boxer, D-Calif., said in an interview. “Now that the benefits are kicking in, it’s a lot easier to explain it.”

Sen. Tom Harkin, D-Iowa, said the court’s ruling lifts a cloud of uncertainty.

“Now the American people are going to say, ‘Now what’s in that for me?”’ Harkin said. “As long as Democrats are willing to go out there and positively say, ‘Look, now you are guaranteed that you will get affordable health insurance if you had breast cancer in the past ... preventive care, free mammograms. ... And they (Republicans) want to take it away from you. You have it now and they want to take it away from you. If you want it taken away from you, you just go ahead and vote for them.”’  

Sen. John Kerry, D-Mass., the presidential nominee in 2004, said Democrats need to seize the chance.

“I think it’s very important to do what wasn’t done sufficiently before,” Kerry said.

The Republican response? Bring it on.

The court ruling gave clarity to the GOP call for repeal — electing Republican candidates in November is the only way now to ensure the law’s demise. In a fundraising appeal within hours of the court announcement, Sen. John Cornyn, R-Texas, said, “Now we know — four seats to repeal Obamacare,” a reference to the net number that the GOP needs to seize the Senate majority.

Republicans also used the ruling to craft a new attack line. Chief Justice John Roberts’ majority opinion said the law’s requirement that Americans purchase health care is a tax, which Republicans argued contradicted Obama and Democrats who insist they aren’t raising taxes on the poor and middle class.

“The court blew the president’s cover,” Senate Minority Leader Mitch McConnell, R-Ky., said.

The tax debate will be at the forefront when the House votes the week of July 9 to overturn the law, a largely symbolic step with a Democratic-controlled Senate but one that will put Democrats and Republicans on record and provide fodder for the campaign.