Russian hackers tried to tamper with voting systems in 21 states during the 2016 US presidential election, and the American intelligence community expects Moscow will try again in November.

But states from Virginia to Rhode Island aren’t focused on new cybersecurity software. Instead, they’re looking to one of the oldest technologies in existence: paper.

It’s a striking change from 2016, when five states used electronic voting systems that didn’t leave any paper record of votes, and nine used some paperless machines. Now, states are rushing to take advantage of $380 million that Congress approved last month to help protect voting systems. Most states are prioritizing some kind of paper record.

“In this year of our lord 2018, we’re talking about paper ballots, but that actually might be one of the smartest systems,” Sen. Kamala Harris (D-CA) told reporters in March.

Paper voting developed a bad reputation after the US presidential election in 2000, when the presidency came down to a handful of votes in Florida. The state used a voting system that punched holes in paper, resulting in the infamous “hanging chads” issue. If the hole wasn’t punched perfectly and the punched-out paper stuck to the sheet, it wasn’t completely clear whether the vote should count.

Congress responded by passing the Help America Vote Act in 2002, which pushed a lot of states to buy electronic voting machines and provided funding for new equipment.

“There was a rush to buy something, anything,” Marian Schneider, the president of Verified Voting, told me. Verified Voting is a not-for-profit that advocates the use of paper voting records.

After 2000, some states turned to systems that were entirely electronic, with machines keeping a tally of votes digitally. Fifty out of 67 counties in Pennsylvania use machines that have no paper printouts at all.

But here’s the problem: If an electronic voting system becomes compromised by Russian hackers, or hackers from another country, and there’s no paper trail to refer back to, then there’s no way to know if vote counts are accurate. It’s also really difficult to prove election tampering took place.

So Congress is encouraging states to move back to paper, even if that just means printing out a receipt after each electronic vote is cast.

“Russia cannot hack a piece of paper,” Harris said.

Russia successfully hacked one state’s voting system and attacked two dozen others

Members of the Senate Intelligence Committee unveiled the first part of their investigation into Russian election meddling in 2016 at a March 20 press conference, which triggered their push for paper ballots.

The committee found that Russia tried to tamper with 21 state election systems and successfully broke into one in Illinois. Illinois state officials said that though Russian hackers gained access to the state’s voter registration system, they didn’t change any vote counts during the election.

Senate Intelligence Committee members approved a set of recommendations for states based on what they uncovered from the election meddling. One of their top suggestions: paper ballots.

Paper ballots are safer because they can’t be changed remotely by hackers and can be recounted after an election.

The committee members also recommended disconnecting voting machines from the internet to prevent hacking, and setting up new safety procedures to make sure that paper ballots are always under lock and key.

If they want to get new voting systems, states can apply for some of the $380 million approved by Congress to improve election security, which was set up as a grant program.

But Intelligence Committee Chair Richard Burr (R-NC) has repeatedly pointed out that the Senate committee doesn’t have any real authority over election issues; states manage voting.

This means that state participation is entirely voluntary, so it’s unclear how effective all this will be. States are often hesitant to work with the federal government on election issues, concerned about federal overreach.

“Congress tries to tiptoe around the issue,” Michael Sozan, a senior fellow at the Center for American Progress, told me. “The federal government is fairly loath to interfere.”

When it comes to elections, states generally like to run the show

States are technically in charge of running elections, not the federal government. And sometimes states get worried about federal overreach in both local and national elections.

Former Secretary of Homeland Security Jeh Johnson told the Senate Intelligence Committee during a March hearing about a phone call he had with the state election chiefs in August 2016. Johnson said he was trying to get states to accept help from the federal government. At the time, federal officials knew that Russia was trying to hack state voting systems, but they weren’t sharing specific information about the threat.

States balked at the idea of federal involvement.

“We really pushed back,” Jim Condos, secretary of state of Vermont, told Congress in March. “I would say that we pushed back, red states and blue states were pushing back because we were looking at potential for federal overreach.”

States have fought against federal involvement since the 1950s, when Southern states South Carolina and Georgia fought federal government interference in their efforts to suppress minority voting.

Doug Jones, a voting expert and professor of computer science at the University of Iowa, told me the resistance to federal involvement has never changed.

“Every time the federal government steps in, it’s [to reduce] the authority and add to the rules that the state election directors have,” he said. “State election directors don’t like having rules. They like to be king.”

But despite their historic aversion to federal involvement, some states have been moving quickly to switch back to paper ballots.

Virginia moved aggressively in 2017 to implement paper ballots. The state was one of the 21 whose networks were attacked by Russian hackers.

When Virginia announced it was moving back to the paper ballot, Sen. Mark Warner (D-VA) told the Washington Post it was important for every state to make the change, because foreign powers will likely target the most vulnerable states to swing an election.

“To make a change, even on the national level, doesn’t require penetration into 50 states,” Warner said. “You could pick two or three states in two or three jurisdictions and alter an election.”

Of course, paper ballots don’t entirely solve the issue of election meddling, as foreign countries can still try to influence voters with false information, like Russia did in 2016. But the simple solution of having paper printouts could help verify that tampering has taken place, and help ensure that US voters are choosing the candidates they want — not hackers.