Midterm voting takes place on Nov. 6., and the totals include donations given through Oct. 16. It doesn't count money that industry groups give to other political committees that ends up in candidates' campaign coffers, or their independent spending on issue ads. Nor does it include state ballot measures, including a California proposal that affects the dialysis industry and has attracted tens of millions of dollars in spending.

The 2018 election is projected to be the most expensive midterm in history, with $5 billion expected to be spent by candidates, parties, PACs and outside groups, according to the Center for Responsive Politics, a nonprofit that compiles data on campaign contributions and lobbying.

About 45 percent of America's $3.3 trillion in annual health care spending comes from government, so the industry has a lot riding on decisions in Congress. The health-care industry has spent less on the election than finance and some other industries, but more than defense, labor groups, and tech companies.

Brendan Fischer, director of federal reform at the Campaign Legal Center, a nonpartisan expert and watchdog for campaign finance, said the money spent each election cycle has consistently escalated over the past decade.

“Our system is increasingly tilted towards the interest of wealthy donors because of the amount of money it takes to mount a legitimate campaign,” Fischer said.

The highest donations from health-care groups and individuals went to races where senators are raising historic amounts of money. The top recipients are Democratic senators Claire McCaskill of Missouri, with $1.85 million from health groups; Bob Casey of Pennsylvania with $1.76 million; and Sherrod Brown of Ohio with $1.74 million. Each has sparred with Republican opponents over the Affordable Care Act and the law's protections for people with pre-existing conditions.

While much of the health-care debate in this election has focused on drug prices, physician groups have contributed more to congressional campaigns than pharmaceutical companies. Their PACs contributed $20.6 million to federal candidates.

The American Association of Orthopaedic Surgeons spent the most of the provider PACs, giving $1.37 million to federal candidates. The group, which gave money to both parties, made its largest single expenditure of $250,000 to the Congressional Leadership Fund, a GOP super PAC.

“Like many other health-care groups, we're having to contribute more this cycle while health care remains a central issue and competitive races are occurring across the country,” said John Gill, chair of the orthopedic surgeons' PAC, in a statement.

Advocates for lower drug prices are also spending heavily. Patients for Affordable Drugs Action, a super PAC backed by the foundation of billionaire John and Laura Arnold, has received almost $10 million in contributions, and spent more than $9 million.

The group has spent $3.3 million against Republican Bob Hugin, the former chairman of drugmaker Celgene Corp. who is running for U.S. Senate in New Jersey. One ad from the PAC claims that Hugin made about $100 million overcharging cancer patients for their medicine.

Nick Iacovella, a spokesman for Hugin's campaign, denied the allegations by Patients for Affordable Drug Action. “Under Bob Hugin's leadership, Celgene put in place the most compassionate patient assistance program in the world,” affording most patients copays under $50, he said in a statement.

UnitedHealth Group Inc. spent the most among the major insurers, with a slight preference for Republican candidates. Anthem Inc., the second-largest spender, gave slightly more to Democrats. Among major insurers, the two companies also gave the most to leadership PACs and campaign committees that the parties use to fundraise. The amounts were split fairly evenly between the parties, according to data compiled by Washington-based GovPredict, a nonpartisan political research firm.

Andrew Mayersohn, a researcher at the Center for Responsive Politics, said the distribution of health-care contributions is almost “squarely in the middle” between typically conservative sectors like construction and more liberal sectors like the media.

“Are they spending because they feel like they need to shape whatever kind of health reform a Republican congress passes?” said Mayersohn. “When those are your considerations, you're not thinking too hard about which party you're giving to. You just want to make sure you have a seat at the table when the bills are being written.”

— With assistance by John Tozzi

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