Tonight's primary elections will include an important referendum on a growing trend: Progressive gubernatorial candidates vowing to implement some form of single-payer at the state level.

What to watch: Michigan's Democratic primary, which will be held tonight, includes Abdul el-Sayed — a progressive candidate (and former Detroit health commissioner) who has said he'll bring "Medicare for All" to Michigan.

No state has ever made single-payer work. But that's not stopping a handful of Democratic candidates from promising to try. The Washington Post's Dave Weigel runs through some of them:

• Maryland's Ben Jealous and Massachusetts' Jay Gonzalez are both campaigning on "Medicare for All" as they try to defeat extremely popular moderate Republican governors in their respective blue states.
• Cynthia Nixon, challenging New York Gov. Andrew Cuomo from the left, has endorsed an expansive health care overhaul there.
• California Lieutenant Gov. Gavin Newsom, who has already won his primary, is also promoting the idea for California.

The problem is money. States would largely have to pay for their versions of single-payer on top of existing federal programs, not instead of them.

• Medicare and the taxes that fund it, for example, are both federal programs that states — unlike the federal government — don't have the power to fold into some other system.

Why it matters: As unlikely as state-level single-payer might be, gubernatorial candidates' embrace of the idea is still a clear sign of where Democrats are headed.

Go deeper: Axios followed el-Sayed last week as he campaigned with newly minted progressive icon Alexandria Ocasio-Cortez.

The average insurance deductible keeps going up, as does the number of people covered by high-deductible plans. And only about half of those people get help from their employers to save up for potential medical bills, according to a new study in Health Affairs.

The details:

• In 2006, just 11.4% of private-sector workers had a high-deductible plan. In 2016, that number was up to 46.5%.
• Roughly half of those workers also get an employer contribution to a health savings account or health reimbursement arrangement.
• High-deductible plans are most popular with smaller companies, where employer contributions to an HSA are least popular.
• At the smallest companies, about two-thirds of workers didn't have the option of a plan without a high deductible, and don't get an employer contribution to an HSA or HRA.

Why it matters: Higher deductibles don't just require people to pay more out of pocket each year. They also expose those consumers to the complexities of the health care system, including the way prices are set.

• People with high deductibles are more likely to have to pay the full sticker price of a prescription drug, or for a hospital procedure.

Also from Health Affairs: The level of competition among insurance companies has affected Affordable Care Act premiums more than any other factor.

By the numbers: Premiums are 50% higher this year in areas with just one insurer than in areas with two insurers.

• “The presence of a monopolist insurer was the strongest, and most precise, predictor of 2018 premiums,” the study says.
• Other factors commonly associated with higher premiums — like hospital concentration and the health of the people who live there — showed significantly smaller effects.

How it works: Jessica Van Parys, the Hunter College economics professor who conducted the study, suggests that insurers underpriced their ACA offerings in the first few years to capture market share, then raised their prices over the years.

• Costs and regulatory uncertainty largely kept new competitors from entering those monopolized markets.

The Food and Drug Administration released new guidance yesterday to expand the use of medication-assisted treatment, or MAT, for addiction.

What's happening: The agency is giving drugmakers additional ways to demonstrate the effectiveness of MAT products, my colleague Caitlin Owens reports.

• Traditionally, MAT drugs' success has been measured based on whether a patient in recovery stopped using opioids.
• The FDA will now give greater weight to reductions in relapse overdoses and infectious disease transmission.

Why it matters: This is a step toward the FDA's goal of a comprehensive approach to the opioid epidemic, with a focus on harm reduction.

• "While existing MAT drugs do improve outcomes, relapse rates are still high. And not all patients respond positively to such medications. #FDA is taking steps to encourage more widespread innovation and development of MAT drugs," FDA Commissioner Scott Gottlieb tweeted this weekend.

Mental health is a big focus at this week's Black Hat cybersecurity conference, Axios' Joe Uchill reports.

The big picture: Black Hat has a large industry presence, and shining a light on topics that tend to be discussed outside the corporate eye — things like suicide, stress load, mental illness and trauma — may force major employers in the field to think about those issues, too.

Mental illness and suicide: "In the past year I know several people in the community have taken their own lives," said Jay Radcliffe of Boston Scientific. "It’s a sad thing, and something I feel responsible to talk about."

• Radcliffe, well known for hacking devices, will be presenting about his own experience with depression with Christian Dameff, an emergency medicine physician.

Go deeper: Subscribe to Codebook, Joe's cybersecurity newsletter.