Thousands of people showed up in freezing temperatures on Sunday in Michigan where Sen. Bernie Sanders called on Americans to resist Republican efforts to repeal President Barack Obama's health care law, one of a number of rallies Democrats staged across the country to highlight opposition.

Labor unions were a strong presence at the rally in a parking lot at Macomb County Community College in the Detroit suburb of Warren, where some people carried signs including "Save our Health Care."

Lisa Bible, 45, of Bancroft, Michigan said she has an auto immune disease and high cholesterol. She says the existing law has been an answer to her and her husband's prayers, but she worries that if it's repealed her family may get stuck with her medical bills.

"I'm going to get really sick and my life will be at risk," she said.

President-elect Donald Trump has vowed to overturn and replace the Affordable Care Act and majority Republicans in Congress this week began the process of repealing it using a budget maneuver that requires a bare majority in the Senate.

"This is the wealthiest country in the history of the world. It is time we got our national priorities right," Sanders told the Michigan rally.

The law has delivered health coverage to about 20 million people but is saddled with problems such as rapidly rising premiums and large co-payments.

Britt Waligorski, 31, a health care administrator for a dental practice, said she didn't get health insurance through work but has been covered through the health law for three years. While the premiums have gone up, she said she is concerned that services for women will be taken away if it is repealed.

"It's done a lot for women for their annual checkups, for mammograms -- women's health in general. If this gets repealed, we're going to go back to the old days when that's not covered," she said.

The health law has provided subsidies and Medicaid coverage for millions who don't get insurance at work. It has required insurers to cover certain services such as family planning and people who are already ill, and has placed limits on the amount that the sick and elderly can be billed for health care.

Sanders, a strong supporter of the law, made several visits to the state last year during the Michigan primary and defeated Hillary Clinton in the state. But in a major surprise, Michigan narrowly voted for Trump on Nov. 8, the first Republican presidential candidate to carry the state since 1988.

Rallies in some other cities in support of the health law also were well attended. Police estimated about 600 people showed up in Portland, Maine. Hundreds also attended a rally in Newark, New Jersey.

Republicans want to end the fines that enforce the requirement that many individuals buy coverage and that larger companies provide it to workers.

But they face internal disagreements on how to pay for any replacement and how to protect consumers and insurers during a long phase-in of an alternative.

Mark Heller, 45, a civil rights, immigration and labor attorney who drove to the Michigan event from Toledo, Ohio, said that stopping Republicans from repealing the law may take more than attending rallies.

"I think that it's going to take civil disobedience to turn this around because they have the votes in both the Senate and the House, and the president," he said.