Governors are preparing to face one of the toughest moral choices they'll confront in office: how to allocate limited stocks of coronavirus vaccine among outsized shares of vulnerable Americans.

Why it matters: Everyone agrees health care workers need to be at the front of the line. But after that things get tricky, as New Mexico's Gov. Michelle Lujan Grisham explained in an interview with Axios.

What they're saying: "It really is all going to depend how much vaccine are we going to have access to, and how quickly," said Grisham, who's also in contention to lead the Department of Health and Human Services in the Biden administration. "If you can't get it done quickly, it's problematic."

• She described a nightmare scenario: The federal government gives her sufficient doses to initially vaccinate every nursing home resident and every hospital worker in her state, but not nearly enough to cover the one in three adults statewide with chronic disorders.
• "So I've got 700,000 people I need to start getting the vaccine to, and I get 25,000 doses," she said. "That will be hard, and what we’ll do is, we'll allocate it per community in the same way we do flu."
• In 2004, as New Mexico's health secretary, she faced the prospect of a flu vaccine shortage and had to draw up criteria for how to prioritize distribution of a limited supply. New Mexico ended up getting all the flu vaccine it needed and didn't have to execute the plan, she said.

The big picture: The Trump administration is leaving it up to governors to decide who gets the vaccine and when. It's an ultimate test of federalism and of each state's executive's ability to act decisively at warp speed as the deaths pile up and struggling businesses face desperate circumstances.

• After health care workers, nursing home residents and first responders, highest-risk populations include seniors, people with certain underlying health conditions and other frontline workers. The number of available doses early on won't cover all those people.
• Governors also will face pressure from major businesses pushing for access to early doses so they can reopen sooner.
• They'll have to figure out how to serve poor, minority communities and others who are skeptical about vaccines. They'll also inevitably have to deal with some wealthy and well-connected citizens trying to cut ahead in the line.