Today's "Super Tuesday 2.0" primaries in six states are a real-time test of how the coronavirus could alter presidential voting — especially in Washington, the state with the largest number of U.S. deaths to date.

The state of play: Washington is a vote-by-mail state, which presents unique concerns and benefits in the face of a health crisis.

Why it matters: "It’s a model for other states about how to handle this," Washington Democratic Party chair Tina Podlodowski told Axios.

Coronavirus presents "a cautionary tale for other states — if they don’t have a robust mail-in ballot system — for what that may mean for people turning up to vote."

State Democratic Party chairs and executive directors "have had a robust conversation" with each other and the Democratic National Committee about how to deal with coronavirus and its potential effects on early voting contests.

Kim Wyman, Washington's secretary of state, told Axios: “Coronavirus really doesn’t affect us in the same way as states that have to open polling places.”

She said that the officials handling the ballots have been instructed to wear gloves while doing so, to change those gloves frequently and to wash their hands frequently throughout the process.

Voters have been advised to use water — not their own saliva — to seal their ballot envelope to minimize any potential spreading of the coronavirus microbes.

Driving the news: Michigan and Washington — the two states with the largest number of delegates in today's contests — represent two important tests of whether Bernie Sanders can regain momentum with Democrats as Joe Biden leads the race toward the nomination. Tulsi Gabbard also remains in the contest.

Missouri, Mississippi, Idaho and North Dakota are the other states voting today.

As the virus spreads, many states and U.S. territories have yet to hold Democratic primaries, with contests running through June. The general election is set for November.

A little over a year ago, Washington state's Democratic Party shifted from its decades-long practice of caucusing to appoint delegates. That change now looks prescient, though disease containment was not the guiding mission at the time.

Voters won't be forced to stand in line for hours to cast their ballot, and they won't be cramming into a high school gymnasium to participate in a caucus.

Washington state has already received five times as many ballots in the 2020 primary than people who caucused in 2016.

Podlodowski told Axios that 1.3 million people had turned in a primary ballot as of last Friday. The ultimate turnout is expected to exceed 1.7 million.

In 2016, she said, 230,000 people caucused in Washington state.

Washington voters must either place ballots in an official drop box or mail them in, postmarked by 8 pm local time.

place ballots in an official drop box or mail them in, postmarked by 8 pm local time. Wyman said that while she’s happy to share best practices with other secretaries of state, “it’s not really an option” for states having primaries in the next three to four months to switch to a mail-in system because of the legal steps it requires.

The big picture: During last week's Super Tuesday contests, the biggest states, California and Texas, got a glimpse of the coronavirus' potential impact on elections. But concerns about the virus have exploded domestically over the past week.

Various precinct openings in Austin were delayed after some officials skipped work over coronavirus fears.

Officials in Solano County, California, added an additional precaution after two health care workers tested positive for the coronavirus: a curbside location where voters could hand over their ballot through the window without ever getting out of their cars.

Oregon has declared a state of emergency over the coronavirus, but similar to Washington, it's a vote-by-mail state. Its primary is May 19.

The bottom line: Washington state is one of only five states with mail-in voting for all elections — and after today, three of them will have already had their contests — so if concerns about public health persist into general election season, most states will have to seriously scramble to try to adapt their systems.