An all-out war over mail voting has erupted in courts across the country. Here’s what’s at stake.

Do you have to request an absentee ballot application, or will one be sent to you automatically? Will your ballot be counted if the mailman is late? If you fill out your absentee ballot wrong, can you fix it?

Questions like these — the fine print of democracy when it comes to mail voting — are at the heart of a record-breaking, high-dollar legal war being waged in courtrooms nationwide, fueled by the coronavirus that’s upended the idea of holding a presidential election as usual and by President Donald Trump’s constant warnings about widespread voter fraud that no one can prove exists.

“This is clearly a historic high,” Trevor Potter, the former commissioner and chairman of the Federal Election Commission and now president of the Campaign Legal Center, a nonprofit watchdog, said of the sheer number of lawsuits tied to vote by mail. “It would have been a contentious fall without the pandemic, but the pandemic changes everything because it has caused so many states to revisit how they vote.”

Substantive change to voter access in multiple states all at once is rare, but this year, officials have pushed to make mail voting easier to help protect people from the coronavirus. Plenty of these changes are happening in the courts — many state legislatures are out of session — as state officials, advocates and partisans duke it out over how to adapt existing election laws to fit a pandemic.

NBC News has reviewed more than 175 suits in 43 states and the District of Columbia contesting everything from whether postage must be prepaid on absentee ballots to where you can vote and how ballots can be legally transported from voters’ hands to election officials. It’s litigation that will decide who can vote in the 2020 presidential election and how, and advocates fear it will perpetuate and exacerbate racial biases that have long been baked into the voting system.

Democrats say they’re trying to make sure every vote counts, and voting rights advocates are raising the alarm that the expansion of existing absentee and mail voting systems could create widespread disenfranchisement and discrimination unless done correctly.

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Republicans argue that last-minute election changes in the courts are improper and create opportunities for voter fraud and foreign interference, despite the fact that there is no evidence of widespread fraud and experts say foreign meddling in mail voting is extremely unlikely. The Republican National Committee (RNC) is litigating in 17 states, backed by a joint budget with the Trump campaign of $20 million earmarked for election-related legal fights and a small army of Election Day poll watchers and attorneys. The Republicans have repeatedly stepped in to defend against suits from advocacy and voting rights groups seeking to adapt election laws to pandemic realities. Justin Riemer, the RNC’s chief counsel, told Axios that the legal work is “on steroids this year.”

Much of voting rights advocates’ litigation is aimed at lowering the absentee ballot rejection rates that have skyrocketed during the primaries.

As many as 64 percent of Americans are expected to vote by mail this year, according to a group of researchers at Harvard, Northeastern and Rutgers universities, as well as the Harvard Medical School, and the litigation currently winding its way through the courts could affect millions of ballots.

“We have this romantic notion that American democracy was designed for American participation. It is not. At its inception, our democracy was that Blacks were not human, Native Americans did not exist, women were to be silent,” said Stacey Abrams, founder of the voting rights advocacy group Fair Fight, which has gone to court in Georgia and is organizing voter protection efforts. “We’ve had to pass three constitutional amendments to have something that approaches actual participation. The flaw in each of those amendments is that it delegates administration to the states.”

And in that administration, advocates and academics alike see discriminatory effects in mail voting systems.

“If you were to design a system that would enfranchise voters that are older and white — at the expense of voters who are younger and more diverse — in many states you would adopt the existing voting laws,” Marc Elias, Democrats’ top elections attorney, told NBC News. He’s working on dozens of lawsuits in 17 states this year.

Here’s what’s at the heart of the suits, and what could change about the rules surrounding vote by mail.

Ballot deadlines

A late ballot is the No. 1 reason an absentee ballot is rejected in America, according to data published in the Election Administration and Voting Survey from 2018 and 2016. In the primary elections, hundreds of thousands of ballots have already been rejected for this reason. The Post Office has reportedly warned state officials that on-time delivery cannot be relied on for mail elections in 46 states and D.C.,including the 2020 battlegrounds Pennsylvania, North Carolina, Nevada, Michigan, Minnesota, Texas and Arizona.

Most states require that election officials receive mailed ballots by a certain time on Election Day, but advocates have sued to get officials to count ballots postmarked on or before Election Day in more than a dozen states.

Fights over ballot receipt deadlines are ongoing in key 2020 battlegrounds, including Wisconsin, Pennsylvania and Georgia. In Minnesota, a court ruled that ballots postmarked on or before Election Day will count — Republicans appealed and the case is ongoing. In Arizona, the state agreed in a settlement to do more voter education and outreach, and to expand early voting to counteract the effects of the deadline. In Michigan, a state Supreme Court declined to hear advocates’ case.

In Pennsylvania, the state responded to a ballot deadline lawsuit by asking the court to extend the deadline to receive postmarked ballots by three days, pointing to a letter from the Post Office saying there was a strong risk of delayed mail service of ballots.

Elias said that by sheer numbers, it’s the most consequential reform states can undertake and pointed to a case he won during Wisconsin’s April primary as a prime example.

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“If you look in the primaries, in Wisconsin the result of us winning that one issue led to 80,000 ballots being counted — that was in the primary and that was one state. It’s going to be hundreds of thousands or millions of ballots that are potentially right on that razor’s edge,” Elias told NBC News.

The Republican National Committee wants mail ballots to be returned to officials by Election Day, and has intervened on behalf of states in several suits regarding ballot deadlines.

And while many states and campaigns will try to counteract the issue of late ballots through voter education — celebrities with major followings like Chrissy Tiegen have also sought to sound the alarm about important deadlines — mail service is not created equal. For rural or very densely populated cities, unreliable mail service is a common issue. The Postal Service also recently announced big changes they say will curb financial losses, but also are reportedly slowing mail service, on top of already reduced hours.

Signed, sealed and…notarized?

More than 50 lawsuits in at least 33 states have been filed this year to address signature issues that have come up as a result of the pandemic, including the challenge of gathering signatures for ballot initiatives when it’s not safe to physically canvas. When it comes to mail voting, however, the process of signature verification is a major one that voting rights advocates want the courts to fix.

States use a variety of mechanisms to verify that absentee voters are who they say they are, most often checking ballot signatures against voters’ registration signatures. It’s a simple and effective security measure, but advocates say there should be standardized processes and voters need recourse for fixing ballot errors, like a forgotten signature.

Democrats and advocacy groups like the League of Women Voters have sued to change or institute “cure” processes in at least 10 states this year. New York’s state Legislature passed a law creating a cure process in July, while Georgia settled a suit with state Democrats to update their cure process after their primary. A North Carolina judge also ordered a cure process for ballots in November.

Thirteen states also require that absentee ballots be signed by a witness or a notary public, or require additional documentary proof like photocopies of a driver’s license. Many of those rules are being debated in the courts as advocates argue witness signatures are a useless requirement that do not prevent fraud while also making it harder to vote by mail — and carries an added element of danger during a pandemic. Missouri election officials have reported incidents of notaries trying to charge voters for the service, a barrier that is illegal under the state’s law.

“Whether or not you think it’s a good idea to have a witness, in a pandemic you absolutely don’t want a witness requirement if someone’s going to have to risk their health,” Potter told NBC News.

Minnesota, North Carolina, Rhode Island and Virginia have dropped or loosened their witness requirements so far. Republicans, who argue witness signatures improve ballot security, unsuccessfully appealed to the U.S. Supreme Court to intervene in the Rhode Island suit, but state Republicans and the Trump campaign did convince a state Supreme Court in Minnesota to hear an appeal of the case.

Helping or harvesting?

Countless voters are assisted by poll workers at their physical polling locations, but a number of states have laws that criminalize helping voters with mail ballots or transporting sealed ballots to a drop-off location.

Republicans, including Trump, argue that collecting ballots can become “ballot harvesting” and is ripe for fraud.

While there’s little fraud in American elections, a Republican operative in North Carolina was charged in what prosecutors say was a scheme to manipulate the outcome of a 2018 congressional race by collecting and sometimes filling out voters’ absentee ballots after they were in his possession. He faces a number of criminal charges, as North Carolina does not allow ballot collection of any kind, and has denied wrongdoing.

Democrats and advocates say ballot collection is just another voter turnout method and have mounted more than a dozen lawsuits seeking to overturn laws prohibiting it in at least eight states. Courts have recently tossed or barred enforcement of rules preventing ballot collection in Arizona and Montana, while Nevada’s state Legislature recently approved the practice. Republicans sued in Minnesota to try to block ballot collection, too.

Some states also allow ballot drop boxes — a popular and relatively cheap way for officials to securely collect ballots — but others prohibit them. Connecticut and Michigan both used drop boxes during the primaries this year, and Michigan officials plan to add more for the general election; Maine is reportedly looking into drop boxes for the general election, as well. Republicans argue these boxes create opportunities for fraud, though it’s unclear how exactly since ballots still need to be reviewed by election officials before they are counted. Substantive fraud does not occur in American elections. In Pennsylvania, the Trump campaign is suing to stop the use of drop boxes, saying that allowing these drop points “eviscerates the procedural protections that currently accompany Pennsylvania’s vote by mail.”

It’s not just drop boxes and ballot collection that has been targeted by Republicans this year, either.

The Trump campaign is also suing election officials who seek to help voters request their ballot. The president’s re-election campaign and the GOP announced lawsuits on Wednesday against two Iowa county officials who opted to proactively fill in voters’ general election absentee ballot applications with identifying information before mailing them to voters.

“This is about the safety of voters,” one of the officials, Linn County Auditor Joel Miller, told a local CBS affiliate, defending the decision. “This is about running an election in a pandemic.”