BISMARCK, N.D. (AP) — Health care has emerged as a major issue in North Dakota's U.S. Senate race, with Democratic U.S. Sen. Heidi Heitkamp and Rep. Kevin Cramer, her Republican challenger, arguing over who will do more for people with medical problems.

In a race seen as critical for control of the closely divided Senate, the candidates are struggling for an advantage and have turned to a component of former President Barack Obama's health care law that forbids health insurers from denying coverage to people with health problems.

Heitkamp, seeking re-election in a heavily Republican state, is one of several Democratic candidates across the country who are highlighting health care as an issue they believe will resonate with voters in the mid-term elections.

On Wednesday, Heitkamp said her opponent wants to kill the popular provision in the Affordable Care Act, while she would work to keep the "good" in it.

"He does not want to keep the good," Heitkamp told reporters on a teleconference. "He wants to throw it all out."

Earlier Wednesday and surrounded by party faithful, Cramer dismissed such claims.

"It's a ridiculous notion that Republicans are not going to protect people with pre-existing conditions," said Cramer, flanked by the state's lieutenant governor, attorney general and insurance commissioner, all Republicans. "It's a myth Republicans don't care about pre-existing conditions."

Cramer said he supports retaining a component that would bar insurance companies from discriminating against people with preexisting conditions but he has been among those in the House who has voted for legislation that would undo much of Obama's health care act.

Heitkamp said her opponent is more interested in "political talking points than solving this problem."

"National Democrats and my opponent are trying to make this issue into a boogeyman," Cramer said in an interview. "North Dakotans aren't buying it."

The campaigns have also sparred over a lawsuit by a coalition of 20 GOP-led states that argues the health care law is no longer constitutional since the Republican-backed tax overhaul eliminated fines for not having health coverage. Cramer supports the lawsuit, which the state of North Dakota joined in June.

Democrats say if the lawsuit succeeds, it would strip protections for thousands of North Dakotans with preexisting conditions.

Cramer said Heitkamp has exaggerated the issue in a recent television ad that features Denise Sandvick from rural North Dakota. Heitkamp says in the ad that Sandvick suffers from heart disease while also mentioning Heitkamp's own battle with breast cancer.

"Like 300,000 North Dakotans, Denise has a pre-existing condition," Heitkamp says in the ad. "That used to mean no health insurance."

Heitkamp on Wednesday clarified the statement.

"In no way did I ever say half the people in North Dakota weren't covered by health insurance," she told reporters.

Heitkamp said she meant that was the number of people who would be in danger of losing pre-existing health coverage.

People with pre-existing conditions could have been denied coverage prior to the Affordable Care Act and could lose it if it's repealed, but one expert said the number at risk of losing insurance is far smaller.

That's because most people have job-based health benefits that typically cover people regardless of pre-existing conditions, said Paul Ginsburg, a health policy expert with the nonpartisan Brookings Institution.

Prior to Obamacare, pre-existing conditions were a roadblock for coverage for people with health issues and who attempted to get an individual insurance policy. They could either be turned away by insurers or charged more, or their policy might not have covered a particular condition, like a recurrence of prostate cancer, for example.

North Dakota has about 755,000 residents.

State Insurance Department data show more than 415,000 North Dakotans are covered through employer health plans, and almost 220,000 are covered by government programs such as Medicare and Medicaid. More than 60,000 are uninsured and another 60,000 are on private insurance, and are most at risk of losing coverage if they lose their jobs and attempt to get another individual plan, especially if they have a pre-existing condition.

"Some will be able to get health insurance and some will not if they have a medical history," Ginsburg said