With hours to go until polls close in Arizona, Florida and Illinois, the Biden campaign is downplaying any concern that low in-person turnout because of the coronavirus outbreak is not representative of the electorate, pointing to early voting numbers to back their point.

“While voter turnout on election day itself may be lower due to COVID-19 concerns, we believe that, with early vote and vote by mail, overall turnout will be roughly on pace for 2016 in Arizona and Florida and roughly on pace for 2018 in Illinois, and that voter turnout in all three states will reflect the population at large,” spokesperson Kate Bedingfield wrote in a campaign memo.  

Pointing to a mix of internal and publicly available early voting data, Bedingfield wrote that Biden's campaign believes it will still “emerge tonight with a bigger delegate lead than we had going into the night." The memo says early voting numbers in the three states are far higher than in 2016. 

Calls are growing for states to expand voting-by-mail options ahead of the November election as the coronavirus pandemic has disrupted in-person voting in primary elections across the country.

Sens. Amy Klobuchar, D-Minn, and Ron Wyden, D-Ore., introduced a bill Monday that would mandate emergency mail-in-voting in all states and the Brennan Center for Justice recommended officials consider "a universal vote-by-mail option” as they respond to the crisis.

The progressive advocacy group Stand Up America, meanwhile, on Tuesday launched a six-figure campaign to pressure Congress to expand vote-by-mail options, the group told NBC News.

The group is running digital ads, sending text messages to the 400,000 people on its SMS list, and creating videos and other social media content to encourage Americans, many of whom are now stuck at home, to call their members of Congress. The campaign has generated about 17,400 calls to Congress within the first few hours.

Primary elections scheduled for Tuesday have created confusion and other issues, with Ohio abruptly closing its polls, despite a court order to the contrary, and Chicago election officials sparing with the state's governor over whether to keep election going as they reported extremely low turnout.

So far, in addition to Ohio, Georgia, Puerto Rico, Louisiana, Wyoming, Maryland and Kentucky have postponed their primaries or canceled in-person attendance. 

Washington, the hardest-hit state by COVID-19 outbreak, was able to proceed with their primary last week in part because it votes entirely by mail, state officials said. The state is one of four — along with Oregon, Hawaii, and Colorado — that have transitioned entirely to mail-in balloting, while the vote-by-mail has increased across the country as more states provide it as an option to voters.

Advocates, who have long argued that sending ballots to voters increases participation in elections, say concerns about crowded places have made the need for remote voting more urgent than ever.

Some measures of Chicago-era voting are showing very low turnout compared to previous elections.

Just over 10,000 Chicago voters had cast a ballot in the first hour of voting, said James Allen, a spokesperson for the city board of elections in a call with reporters on Tuesday.

“We had extremely low turnout,” Allen said, adding, “We also suspect there is a lot concern about going to any public place with more than 10 people."

In nearby DuPage County, fewer than 45,000 voters had cast their ballots as of noon Tuesday, the county said, on pace for a sharp decline from its turnout last election. The county already had nearly 49,000 recorded ballots cast in early voting or by mail; in the 2016 primary, it recorded almost 290,000 total votes.

Tuesday's results were "remarkably low,” said Matt Dietrich, spokesperson for Illinois' board of elections. He expects similar results statewide. “When we get the official numbers, I seriously doubt that we’re going to have anything close to the 33 percent average that we’ve had since 2000 in presidential primaries,” he told NBC News.

Chicago's board of elections had called for Illinois to delay of its primary amid the coronavirus outbreak, Allen said. But Dietrich said state law only allows such a delay by a lawsuit, something the state board was not inclined to pursue.

Illinois Gov. J.B. Pritzker's press secretary said Tuesday that the governor did not want to "risk confusion and disenfranchisement in the courts." "No one is saying this is a perfect solution," his press secretary, Jordan Abudayyeh, said. "We have no perfect solutions at the moment. We only have least-bad solutions."

Because of the coronavirus outbreak, the National Election Pool did not conduct in-person exit polls for Tuesday's primaries.

Instead, the National Election Pool, which includes NBC News, conducted a primary poll — a survey of voters conducted by telephone before Tuesday's vote. The survey asked who respondents would vote for and included questions to help explain voter attitudes and demographics, as an exit poll would. 

Check back throughout the night for results from the NBC News Primary Poll. 

Democrats in three states will hold primaries Tuesday in the first big day of voting since the coronavirus upended vast swaths of American life and was declared a national emergency.

It is uncharted territory for Arizona, Florida and Illinois, which collectively award 441 delegates to the Democratic convention, more than one-fifth of what’s needed to clinch the nomination. Joe Biden leads Bernie Sanders by about 150 delegates, according to the latest NBC News count.

Here are five things to watch for on Tuesday.

Three states are holding Democratic primaries Tuesday -— the first since the coronavirus was declared a pandemic and a national emergency, paralyzing much of the country with shutdowns.

There were initially four states slated to vote, but Ohio's primary was called off Monday night after Gov. Mike DeWine filed suit to block it, citing concerns that poll workers could be exposed to the virus.

The St. Patrick's Day primaries are also the first since Joe Biden and Bernie Sanders faced off in a stripped down, one-on-one debate in Washington, D.C., on Sunday night.

Sanders faces an uphill battle in Tuesday's states — Hillary Clinton won all three while running against him in 2016, and won Ohio as well. Polling shows a possible Biden sweep.

Here's a look at what you need to know.