The same strong majority supports the law's system of insurance marketplaces -- such as HealthCare.gov -- in which people who don't get coverage through an employer can shop for health plans.
And 80 percent of Americans favor the government subsidies provided through the law to help low- and moderate-income people buy insurance.
GOP leaders have called for major cutbacks in Medicaid and a fundamental change in insurance rules that would only guarantee coverage for people who didn't have gaps in coverage. Republicans also would no longer require insurers to offer basic benefits.
Democrats plan to prominently feature people who stand to lose some of these protections if the law is scrapped.
President Barack Obama, in an interview last week with Vox, mentioned Natoma Canfield, a cancer survivor who struggled to obtain affordable insurance before the law was enacted.
"When most people, even if they're not Obama supporters, hear Natoma's story or the stories of other people who have been helped, they know it's wrong to just take away their health care," Obama said. "And it becomes less about who's winning here in Washington. It becomes about how are we doing right by our fellow Americans."
At a meeting with congressional Democrats last week, the president encouraged lawmakers to look at the successful approach the nascent tea party movement took in 2009 and 2010 against Obamacare -- including flooding lawmakers' town hall meetings in their districts.
Also aiding the Obamacare defense could be the GOP's interest in making broader changes to other popular safety net programs, including Medicaid and Medicare.
Medicare provides coverage to more than 50 million elderly and disabled Americans. And Medicaid covers more than 70 million poor children, adults and seniors, many of whom depend on the program for nursing home coverage.
Leading Republicans -- including House Speaker Paul Ryan, R-Wis., and Rep. Tom Price, R-Ga., Trump's pick to be HHS secretary -- have advocated major cuts in the programs that would likely slash coverage for the poor and shift more health care costs onto seniors.