Workers for health care giant Kaiser Permanente Colorado started voting Monday on whether to go on strike this fall.

If they did authorize a walk out, it could impact thousands of frontline workers and about 45 percent of Kaiser’s Colorado workforce.

Kaiser employs more than 7,300 Colorado employees, including physicians. About 3,300 are represented by the Service Employees International Union Local 105, according to a Kaiser spokesperson. The union represents workers in a variety of fields, including phlebotomists, medical assistants, member services staff, clerical workers, technologists and couriers.

A strike could have a considerable impact on both workers and patients. Kaiser is far and away the largest private health insurer in Colorado. It has 640,000 members, according to a Kaiser spokesperson, and nearly 27 percent of the private health insurance market in 2017, the year with the latest available data, according to the Colorado Health Institute. That’s more than double the next biggest insurer, Anthem.

Votes will happen through mid-September. A coalition of 85,000 union workers at Kaiser Permanente facilities nationwide are taking part in the vote. The union says if it's approved it would be the largest private sector work stoppage in the US in more than two decades.

“My own opinion, I’d say 100 percent we’ll go on strike,” said DJ Martinez, a medical assistant who works at Kaiser’s Westminster facility and has been with the company for 22 years.

Martinez is a long-time union member and leader. During a recent rally at the local union hall, Martinez was surprised by the response when cards were handed out and signed to indicate approval of a strike.

“I was shocked at how many signed those when we passed them around,” she said.

The union argues the health care provider's facilities are understaffed and under-resourced. “All we’re asking for is reasonable cost of living increase,” Martinez said. “It’s not unreasonable.”

She said a key sticking point in negotiations is an annual cost of living increases. Also, the union wanted a 3 percent raise and Kaiser was offering just 1 percent.

Kaiser declined an interview request. Spokesperson Nick Roper said in an email that the current proposal includes guaranteed wage increases of 1 percent in 2019 and 2 percent each year from 2020 through 2022.

In a statement, Kaiser said its proposal to union leadership would provide annual pay increases, “that would keep our employees compensated competitively and maintain excellent benefits. Contrary to the union’s claims, there are no pay cuts and no changes to our employees’ pension benefits under our most recent proposal.”

Kaiser defended its proposal, saying it offered “solid” wage increases, opportunities for new hires, retirement security, career mobility and affordable health care.

Kaiser’s labor situation is a complex one. A rift emerged in the coalition of Kaiser unions last year. A number of smaller unions, including those representing nurses, split from the Service Employees International Union over how aggressive a strategy should be to pursue in negotiations with Kaiser.

Recently, Kaiser pushed back against what it called “an adversarial, destructive approach as part of their bargaining strategy.”

Physicians aren't unionized. They belong to the for-profit Colorado Permanente Medical Group.

What a strike could mean for Kaiser’s patients isn’t clear. Martinez said if there were a strike, she thought potentially 80 percent of its members would walk out. That could force Kaiser to make hard decisions, including perhaps shutting down some offices and clearly impacting patients.

“Would (Kaiser) herd (patients) to bigger clinics? That could happen. I’m sure they will have longer waits,” Martinez said.

Both sides say they want to put patients first.

“It is important to understand that a strike vote does not mean that a strike is imminent, although it does place Kaiser Permanente in the position of having to spend millions of dollars preparing for the threat of a strike event,” Kaiser’s statement said. “Our first priority is always continuity of care for our patients and members.”

To Martinez, a strike would help patients’ care.

“It’s not just for us, it’s for our patients,” Martinez said. “We have to do the right thing.”