On the presidential campaign trail, Republican Mitt Romney has repeatedly called for repeal of the 2010 health law and President Barack Obama has vowed to implement it. Yet both men could face obstacles: Romney may be stymied by the lack of a majority in Congress to do his will and Obama could be forced by fiscal concerns or public opinion to revamp parts of the law.

Here is a look at how Obama and Romney might change the health law in the years ahead based on interviews with health policy experts.

OBAMA'S CHALLENGES

President Barack Obama waves to an audience of about 15,000 supporters during a campaign rally in Virginia (Photo by Chip Somodevilla/Getty Images).

President Barack Obama has urged voters to re-elect him so that he can put the law fully into effect. But some analysts predict the mounting pressures to reduce federal spending will complicate that plan.  And others note that in a second term, Obama may be more open to working with Congress to tweak provisions of the law that have raised concerns. Leading up to this tight election, Obama and Democrats have been reluctant to make modifications to the law, known as the Affordable Care Act (ACA).

"Right now (Democrats) can’t criticize the ACA. It’s just not politically smart," said Dan Mendelson, chief executive of the consulting firm Avalere Health who oversaw health programs at the Clinton administration’s Office of Management and Budget. But should Obama win a second term and Democrats retain control of the Senate, "I think that adjustments are on the table" as part of a larger deal to reduce the federal deficit, he said.

Scale Back Subsidies: As part of that effort to reduce federal spending, there could be pressure to scale back the health law’s subsidies that help low-income residents afford coverage. People who earn up to 400 percent of poverty — currently about $92,000 for a family of four — are eligible to get financial help in purchasing coverage.  Another big-ticket item is the expansion of Medicaid coverage to anyone up to 133 percent of the poverty level, or about $30,656 for a family of four.

The ACA is "so vast that by default it has to be impacted if there is a bipartisan, grand bargain debt deal," said Mike Tuffin, managing director of the consulting firm APCO Worldwide’s Washington, D.C., office and formerly executive vice president of America’s Health Insurance Plans, an insurance industry trade group. "You can imagine the subsidies being impacted, the Medicaid expansion being impacted."

Changing the law’s implementation schedule is wishful thinking among Republicans, Mendelson said. Any delay in full implementation could risk political backlash from consumers, who have waited years for the major provisions of the ACA to kick in. Delays may also open the law to other changes that Obama and Democrats don’t want.

"My feeling is that it would be a major political liability for the president to encourage delay," he said, "and that if this is going to be his legacy, I see no indication from the policy makers that they either want or expect there to be a delay."

The president "is willing to work with anyone with good ideas to improve the Affordable Care Act.  What he is not willing to do is reopen old partisan battles over the central guarantees of Obamacare," said Adam Fetcher, a spokesman for the Obama campaign.

Change in Age Rating Bands: The ACA prohibits insurers from charging more than three times as much for a policy sold to an older person than to a younger person. (This does not affect people over 65 who are covered by Medicare.)  This is a change from current law in most states where there are no limits on how much more insurers can charge older people. America’s Health Insurance Plans is advocating that the law’s rating bands be changed to 5:1 to prevent what the group describes as “rate shock” for younger people and families.