SIOUX FALLS, S.D. — U.S. Senate candidate Rick Weiland said Tuesday that Medicare is so efficient and popular among the elderly that he wants to open it to all Americans.

Weiland, the sole Democrat running for the seat being vacated by Sen. Tim Johnson, pledged to introduce legislation letting anyone of any age the opportunity to buy health insurance from the government program. He argues his plan, which he dubs the Medicare Choice Act, could change the behavior of private insurers by creating a true public-private competition, he said during a news conference in Sioux Falls.

"By expanding the pool of insured to younger, healthier Americans, this proposal will strengthen the current Medicare system," Weiland said.

Weiland's five Republican opponents, former Gov. Mike Rounds, Stace Nelson, Larry Rhoden, Annette Bosworth and Jason Ravnsborg, want to repeal the Affordable Care Act championed by President Barack Obama.

Larry Pressler, a former Republican U.S. senator running as an independent candidate, said he would have voted against President Barack Obama's health care law, though he believes it needs to be replaced and not just repealed.

Weiland said his proposal would not require any citizen to give up health insurance. Rather than fining those who fail to purchase a policy, his plan would give those people a minimum Medicare policy.

The proposal also would require that Medicare negotiate with drug companies to get the best possible prescription prices. The Affordable Care Act would have contained such a provision if not for the insurers and drug companies throwing so much money into the political process, he said.

"We would have gotten better health care reform had it not been for the influence of big money, big health insurance companies and the big pharmaceutical companies that didn't want a Medicare-type option to compete with," Weiland said.