You go to businesses and say "You're going to have to pay a big employer paid payroll tax, but in exchange, you get to drop your share of insurance premiums" (average of $15K for family plans, $7K for individual plans). At those costs, even a 15% employer paid payroll tax would be less than the cost of insurance. And with a 15% across the board payroll tax, you'd raise nearly $1.5 trillion. Add in medicare taxes and you start getting close to $2 trillion to go fund universal heathcare. Total healthcare spending is $3.5 trillion, but our spending per capita/per $ of GDP is 2x the rest of the developed world, so you force the issue by cutting reimbursement rates way back... think medicare reimbursement rates, but less.

Heck, Bernie or Warren could even get all red in the face and angry and pound the table about how they're going to make big business pay their fair share and universal insurance will be 100% funded by evil businesses. I think most businesses would go along with the plan (it would lower their costs), and the Bernie Bros would love the fact that they think they're sticking it to big business.

I think the people who would be the most hurt by this would be the health insurers... tough shit, and small businesses who do not currently offer insurance. BUT... most small businesses that don't currently offer insurance fail to do so because of the high cost of insurance relative to the low cost of their employees. If you're paying someone $10/hour and a family plan costs you $15K per year... that's 75% of the cost of your employee's wages. But If everyone now owed a 15% payroll tax to fund universal care, that $10/hour cost now goes to $11.5... yes, a 15% increase, but not a disastrous increase like full employer sponsored insurance would be.