The 2020 election will likely be different thanks to the new coronavirus. In fact, COVID-19 has already left its mark on the Democratic nomination race, with many states postponing their primaries.

So it’s likely that in the coming months, states will begin to move toward allowing more voters to mail in their ballots, or at least cast votes early to spread people out. It’s entirely possible that Election Day 2020 will be more like Election Month (or perhaps months, depending on how long it takes to count the ballots).

That means between now and November, states and election administrators are going to have to make lots of decisions about how they conduct elections. How they manage this may affect who votes and whose vote is counted, how campaigns operate, and perhaps even the level of uncertainty in the polls. In short, the mechanisms of the voting process may turn out to be as important this year as what the candidates say.

We’re not starting from scratch, however. In 2016, roughly two in five voters cast their ballots early or by mail, which marked a record share of ballots cast by methods other than in person on Election Day.

Political scientist Paul Gronke has called this transformation a “quiet revolution,” as over the last several decades, voting in America has gone from being a unique one-day mega-social experience to more and more of a multi-week and increasingly individualized affair. And 2020 may mark a sharp turning point, where one-day in-person voting becomes a relic of the past, like landlines and cassette tapes.

Some quick history of the revolution up till now: Until the late 1970s, pretty much all voting happened on Election Day, with the main exceptions being military personnel, who were allowed to cast absentee ballots. But in 1978, California became the first state to let any voter request a mail-in ballot for any reason. And many other states followed suit.

Flash forward to today, and five states have switched to full vote-by-mail. Oregon became the first in 2000, following a 1998 statewide referendum. Washington (2011) and Colorado (2013) joined more recently, followed by Utah and Hawaii. Other states, especially in the South, have expanded in-person early voting, with Texas starting the trend back in 1987. But there are still a number of states that will need to play catch-up if the November election relies heavily on remote voting. In total, 10 states lack any type of early voting option and 17 states lack no-excuse absentee balloting, meaning they have limited experience handling mailed ballots.

The potential effects on 2020 are hard to predict from past elections, though. On balance, early voting appears to have raised turnout a little, at least in some places — but only by a few percentage points, and with no clear advantage to either party. But results vary, both by which group of voters you’re looking at and by the type of election. Turnout, for instance, has increased most among older people who tend to vote at the highest rates already. And turnout has generally gone up most in lower-profile elections, like primaries and off-year contests. But the effects on general elections are more limited, perhaps because more people already tend to vote in them.

So on one hand, the move to an expanded voting period may not shake up 2020 that much, as most voters do so habitually. That is, most people who vote in any election vote in almost every election. And most people who don’t vote in any one election don’t vote in almost any other election.

Let’s start with the voters who never vote. Many of them are checked out of politics. Or they think their vote doesn’t matter. Or they’ve never voted. Convenience, in other words, isn’t necessarily the issue. So don’t expect them to start voting even if states expand their early-vote offerings.

On the other hand, the people who always vote are, on average, better educated, older, wealthier and more partisan. That means they’re more likely to have some predictable free time and more likely to have made up their mind before Election Day, so they’ve typically been the people most likely to take advantage of the added convenience of early voting. Mailing in a ballot is convenient if you know who you want to vote for and can easily keep an eye on the ballot submission deadline. Conversely, studies have found that lower-income voters and younger voters have a harder time with voting by mail and are more likely to vote on Election Day. Their ballots have also been rejected at higher rates.

This doesn’t mean this gap in early voting is inevitable, especially if early voting efforts were expanded in response to a health crisis like the coronavirus. But closing the gap we currently see in early voting does probably depend on whether states put in the extra effort to make sure that everyone’s vote gets counted. This means making sure voter registration lists have current addresses, ballots are processed in a timely fashion so voters can correct mistakes before it might be too late, and making it easy for citizens to follow the progress of their ballots.

And this is where partisan politics intrudes: The coronavirus stimulus bill currently on the table appears to include $400 million for election support, which may not be enough to help states fully transition to voting by mail. (Democrats were initially demanding $4 billion to expand voting access; the Brennan Center estimated it would cost about $2 billion to implement voting reforms.) So states and local jurisdictions must not only find extra funding, they’ll also have to decide on their own rules, which requires a number of choices be made. For instance, how much of a second chance do election administrators give voters who mess up their ballots? How much do they do to ensure everyone is on the voter rolls, even if they’ve moved recently? Or how do election administrators monitor potential fraud?

How states decide to act could have huge consequences, too, for whose votes get counted and how quickly.

Turnout will certainly depend on how states roll out new programs and how much they invest in ensuring every vote gets counted. But it will also depend on political campaigns, which are the primary educators of voters. Rather than focus on massive last-minute “get out the vote” efforts, campaigns may spread out their efforts over a longer period, and the campaigns that can best track who has voted already and who still needs to vote will have a significant advantage.

Campaigns may also start to place an even greater effort on mobilization than persuasion, since mobilization will be easier to track. This could have significant effects on the kinds of campaigns candidates run (even more partisan, and more micro-targeted). And if states don’t do adequate voter education (expect quality to vary), more responsibility will fall on campaigns to fill in the gaps, which could further exacerbate the divides in our hyper-partisan politics.

There is the question, too, of when we’ll know who won. In a close election, it might take weeks to ensure an accurate final count. Consider how long California — a state with experience handling mail-in ballots — is taking to count ballots from its primary. Given widespread expectations of a high-turnout and closely contested election at a time when our electoral system is already facing a broad legitimacy threat (don’t forget about the possibility of foreign meddling!), room for error is small.

The experience voters have in 2020 could have long-term effects. Presumably most voters, especially the most engaged and active, will like the convenience of mailed ballots or early voting. And once states put these systems in place, officials will likely be under pressure to keep them in place — even if they start out as temporary or provisional.

Then again, it’s also possible the rollout could be a disaster, akin to Iowa’s caucuses this year, and states quickly move away from mail-in voting. We don’t know.

But the former possibility — that citizens mostly like the experience and want to keep it — seems likely. If so, what has long been a slow and steady revolution in early voting would get a sudden, tremendous boost.

If 2020 does deliver the high levels of turnout that were predicted before all the coronavirus protections were put in place, many citizens’ first experience voting could be through the mail rather than in person. If they become habitual voters, they might well become lifetime users of mail-in ballots. And if previous trends in mail-in voting hold, that could mean we’ll see higher turnout in traditionally lower-turnout elections, like primaries, which tend to get the biggest boost from more convenient voting methods.

But for now, the simplest takeaway may just be that a potentially massive and difficult-to-administer change in how people vote adds an extra level of uncertainty to our ability to predict the outcome of the 2020 election.