This post was first published on July 23, 2012.

Voter ID laws are a contentious issue in the 2016 presidential election cycle. Many of the statutes will have their first test at the polls this year. Supporters say the laws — which 36 states have now enacted in some form — are needed to combat voter fraud, while critics see them as a tactic to disenfranchise voters.

We’ve taken a step back to look at the facts behind the laws and break down the issues at the heart of the debate.

So what are these laws?

They are measures intended to ensure that a registered voter is who he says he is and not an impersonator trying to cast a ballot in someone else’s name. The laws, most of which have been passed or strengthened in the last five years, require that registered voters show ID before they’re allowed to vote. Exactly what they need to show varies. Some states require a government-issued photo, while in others a current utility bill or bank statement is sufficient.

As a registered voter, I thought I always had to supply some form of ID during an election.

Not quite. Per federal law, first-time voters who registered by mail must present a photo ID or copy of a current bill or bank statement. Some states generally advise voters bring some form of photo ID. But prior to the 2006 election, no state ever required a voter to produce a government-issued photo ID as a condition to voting. Indiana in 2006 became the first state to enact a strict photo ID law, a law that was upheld two years later by the U.S. Supreme Court.

Why are these voter ID laws so strongly opposed?

Voting law opponents contend these laws disproportionately affect elderly, minority and low-income groups that tend to vote Democratic. Obtaining photo ID can be costly and burdensome. While many states with strict laws offer a free state ID for people without any other way to vote, these IDs require documents like a birth certificate that can cost up to $25 in some places. According to a study from NYU’s Brennan Center, 11 percent of voting-age citizens lack necessary photo ID while many people in rural areas have trouble accessing ID offices.

A lawsuit filed against Alabama in early December 2015 cites the example of a high schooler who can’t vote because she lacks a driver’s license. According to the suit, she needs to get a state issued voter ID at the DMV, but the one nearest to her is only open one day per month and there’s no public transportation to another DMV 40 miles away roundtrip.

During closing arguments in a 2012 case over Texas’s voter ID law, a lawyer for the state brushed aside geographical obstacles as the “reality to life of choosing to live in that part of Texas.”

Former Attorney General Eric Holder and others have compared the laws to a poll tax, in which Southern states during the Jim Crow era imposed voting fees, which discouraged blacks, and even some poor whites — until the passage of grandfather clauses — from voting.

Given the sometimes costly steps required to obtain needed documents today, legal scholars argue that photo ID laws create a new “financial barrier to the ballot box.”

Just how well-founded are fears of voter fraud?

There have been only a small number of fraud cases resulting in a conviction. A New York Times analysis from 2007 identified 120 cases filed by the Justice Department over five years. These cases, many of which stemmed from mistakenly filled registration forms or misunderstanding over voter eligibility, resulted in 86 convictions.

There are “very few documented cases,” said UC-Irvine professor and election law specialist Rick Hasen. “When you do see election fraud, it invariably involves election officials taking steps to change election results or it involves absentee ballots which voter ID laws can’t prevent,” he said.

An analysis by News21, a national investigative reporting project, identified 10 voter impersonation cases out of 2,068 alleged election fraud cases since 2000 — or one out of every 15 million prospective voters.

One of the most vocal supporters of strict voter ID laws, then-Texas Attorney General Greg Abbott (now the state’s governor), told the Houston Chronicle in July 2012 that his office has prosecuted about 50 cases of voter fraud in recent years. “I know for a fact that voter fraud is real, that it must be stopped, and that voter id is one way to prevent cheating at the ballot box and ensure integrity in the electoral system,” he told the paper. Abbott’s office did not respond to ProPublica’s request for comment.

How many voters might be turned away or dissuaded by the laws, and could they really affect the election?

It’s not clear.

According to the Brennan Center, about 11 percent of U.S. citizens, or roughly 21 million citizens, don’t have government-issued photo ID. This figure doesn’t represent all voters likely to vote, just those eligible to vote.

A 2012 analysis by Reuters and research firm Ipsos of data culled from 20,000 voter interviews found that those lacking proper ID were less likely to vote anyway, “regardless of state law changes.”

Among those who said they were “certain to vote,” only 1 percent said they did not have proper ID while another 1 percent said they were uncertain whether they had the proper ID. The analysis also found that those who lack valid photo ID tended to be young people, those without college educations, Hispanics and the poor.

Much of the academic literature finds that voter ID laws have an outsize effect on minorities: A working paper from researchers at the University of California, San Diego found that states with a strict photo ID law saw a significant decrease in turnout among minority and immigrant voters and an increase in the participation gap between white and nonwhite voters.

Exact state figures on how many people lack acceptable IDs can be hard to nail down. Before Pennsylvania’s voter ID law was struck down, a 2012 analysis of state records by the Philadelphia Inquirer found that nearly 760,000 registered voters , or 9.2 percent of the state’s 8.2 million voter base, don’t own state-issued ID cards. State officials, on the other hand, placed the number between 80,000 and 90,000.

In a 2012 trial over Wisconsin’s voter ID law, the plaintiff estimated that about 300,000 voters didn’t have ID and attempted to analyze the demographic breakdown. An expert for thedefense put the number between 100,000 and 300,000 and called the demographics an “open question.”

As for the potential effect on the election, one analysis by Nate Silver at the New York Times’ FiveThirtyEight blog estimates they could decrease voter turnout anywhere between 0.8 and 2.4 percent. It doesn’t sound like a very wide margin, but it all depends on the electoral landscape.

“We don’t know exactly how much these news laws will affect turnout or skew turnout in favor of Republicans,” said Hasen, author of The Voting Wars: From Florida 2000 to the Next Election Meltdown. “But there’s no question that in a very close election, they could be enough to make a difference in the outcome.”

When did voter ID laws get passed — and which states have the strictest ones?

The first such law was passed as early as 2003, but momentum has picked up in recent years. In 2011 alone, legislators in 34 states introduced bills requiring voters show photo ID — 14 of those states already had existing voter ID laws, but lawmakers sought to toughen statutes, mainly to require proof of photo identification.

The National Conference of State Legislatures has a helpful breakdown of states’ voter ID laws and how they vary.

Indiana, Georgia, Tennessee, Kansas, Mississippi, North Dakota, Virginia, Wisconsin and Texas have the toughest versions. These states won’t allow voters to cast a regular ballot without first showing valid photo ID. Other states with photo ID laws offer some more flexibility by providing voters with several alternatives.

What happens if a voter can’t show valid photo ID in these states?

These voters are entitled to a provisional ballot. To ensure their votes count, however, they must produce the mandatory ID within a certain time frame and affirm in person or writing they are the same individual who filled out a temporary ballot on Election Day. The time limits vary: They range anywhere from up to three days after the election (Georgia) to noon the Monday after the election (Indiana).

Are there any exceptions to the photo ID requirement?

Yes: Indigency or religious objections to being photographed. In Indiana, voters will be given a provisional ballot and must sign an affidavit for their exemption by a certain date. Texas grants an exception to voters who don’t have an ID because of a recent natural disaster. For a more specific breakdown of all exceptions, see this list.

Voter ID laws were a big story in 2012. Why are we still talking about them?

A few reasons. While a majority of the voter ID laws were passed before the 2012 election, not all of them went into effect immediately. Wisconsin’s voter ID law, passed in 2011, was only in effect for a low-turnout primary in a few municipalities before getting tied up in court and will have its first major test in 2016. States such as Virginia, Texas, and North Carolina passed voter ID laws after 2012 that haven’t yet been tested in a high-turnout presidential election (Virginia and Texas’ 2013 laws were in effect for the states’ 2014 midterm elections, but North Carolina’s voter ID law hasn’t yet been in effect for a federal election).

This election cycle is also the first presidential election without Section 4(b) of the Voting Rights Act in effect. In 2013, it was struck down in a 5–4 Supreme Court decision, Shelby County v. Holder. States previously required to get preclearance from the Justice Department to change voting laws under a formula laid out in Section 4(b) no longer have to. This means there’s a whole spate of new voting laws in effect. Texas, for example, was initially blocked from implementing its voter ID law until it received preclearance. But the day of the Shelby ruling, the state announced that the law would take effect.

It also means that it’s harder to challenge laws. The Justice Department can still challenge laws for discriminatory voting practices under Section 2 of the Voting Rights Act. But the plaintiff carries the burden of proof under Section 2 challenges, making them harder to win.

“This is the first presidential election in more than 50 years of the Voting Rights Act that the department’s ability to enforce the act has been so severely cut back,” Vanita Gupta, the head of the Justice Department’s civil rights division, told The Washington Post the week before Super Tuesday.

Legal challenges to the laws — from groups like the NAACP, League of Women Voters, and Democratic lawyers — are still winding their way through the legal system. In many states, these cases aren’t the first time the laws have been challenged.

What are the current challenges to the laws?

Some voter ID laws have been blocked by the courts. A Pennsylvania judge struck down the state’s voter ID law in 2014, and the then-governor declined to appeal the ruling to the state Supreme Court.

Marc Elias, a Democratic lawyer who also serves as general counsel for Hillary Clinton’s presidential campaign, brought suit against voter ID laws in Virginia, Wisconsin, Ohio and North Carolina (Elias isn’t acting on behalf of the Clinton campaign). In Virginia, Elias is arguing that the law is an undue burden on poor and minority voters who are unlikely to have an ID and are more likely to vote Democrat.

The NAACP Legal Defense Fund sued Alabama over its voter ID law in early December, alleging it discriminated against African Americans. A judge declined to issue a preliminary injunction on Feb. 18, but hasn’t yet ruled on the suit.

Texas’ voter ID law is in a legal tangle: in August 2015, a federal appeals panel found that the law discriminated against minorities, but it disagreed with the lower court’s finding that the law was the equivalent of a poll tax and intentionally discriminatory. The appellate court sent the law back to the lower court for review. In March 2016, the federal appeals court decided to hear a challenge to the law en banc — the whole court, not just the panel, will hear the case. Meanwhile, the law remains in effect.

Are there other voter ID laws in effect that ask for but don’t necessarily require photo ID?

Yes. In these so-called “non-strict photo ID states” — Florida, Louisiana, Michigan, Idaho, South Dakota and Hawaii — individuals are requested to show photo ID but can still vote if they don’t have one. Instead, they may be asked to sign affidavits affirming their identity or provide a signature that will be compared with those in registration records.

Why has there been such a recent surge in voter ID legislation around the country?

This report by NYU’s Brennan Center for Justice cites primarily big Republican gains in the 2010 midterms which turned voter ID laws into a “major legislative priority.” Aside from Rhode Island, all voter ID legislation has been introduced by Republican-majority legislatures.

News21 also has this report on the close affiliation between the bills’ sponsors and the conservative nonprofit group, American Legislative Exchange Council (ALEC).

Republican figures have championed such laws. In a now-infamous remark, Mike Turzai, majority leader of the Pennsylvania House of Representatives, praised the state’s legislative accomplishments — including passing a voter ID law — at a 2012 Republican State Committee meeting.

“Voter ID, which is gonna allow Governor Romney to win the state of Pennsylvania, done,” he said.

A spokesman for Turzai, Steve Miskin, told ProPublica that Turzai was “mischaracterized” by the press. “For the first time in many years, you’re going to have a relatively level playing field in the presidential elections” as the result of these new laws," Miskin said.

Clarification Sept. 25, 2012: This post has been clarified to reflect details about who was discouraged from voting under a poll tax.