Other states holding primaries on Tuesday, including Massachusetts, Maine and Vermont, predominantly use the technology that most experts consider the most secure: paper ballots that voters fill out by hand.

Here’s a look at how the 14 Super Tuesday states compare:

At risk

Tennessee and Texas represent the biggest election security concerns on Tuesday. Many counties there still use machines that do not produce individual paper vote records, which cybersecurity experts consider an essential protection against hacking and malfunctions.

For instance, voters in Shelby, Tenn., the state’s largest and most populous county and home to Memphis, will use a touchscreen model called the Dominion AccuVote TSx that experts say has serious security flaws. Those concerns prompted voters to sue in 2018 to have the equipment replaced. In September, a federal judge dismissed the case, ruling that residents failed to show evidence of harm.

Several other large Tennessee counties, including Davidson and Williamson, recently purchased paper-based voting machines. But many smaller counties still didn’t have enough money or time to replace their paperless equipment before the presidential primary, even though Congress gave states $380 million in federal election security grants in 2018. In some cases, local officials have simply refused to acknowledge their voting machines are vulnerable.

Texas faces a similar problem: As POLITICO reported last year, dozens of small counties there lack the resources or willingness to replace their insecure machines, and the state Legislature recently punted on mandating paper-based systems until at least 2021.

Some large Texas counties have recently purchased paper-based devices, including Dallas, Tarrant, Bexar and Collin. But paperless machines will remain in use in Harris County, the state’s most populous jurisdiction, which includes Houston.

In Oklahoma, meanwhile, the vast majority of voters will manually fill out paper ballots. But voters with disabilities will be offered the Hart eScan A/T, a device that does not produce individual paper vote records. Oklahoma’s election office has denied this fact — although POLITICO independently confirmed it with two security experts — and does not plan to replace these machines.

Problematic

A few Super Tuesday states will use paperless devices that have been modified with printer attachments meant to provide what’s known as a voter-verified paper audit trail. Security experts consider these printers a temporary fix for paperless machines but urge officials to buy modern devices built around paper ballots as soon as possible.

These states include Arkansas, where some counties will use Election Systems & Software’s paperless iVotronic machine with a printer attachment, although a few jurisdictions have replaced those machines with modern systems. Similarly, some people in Salt Lake County, Utah, will use a printer-enabled Dominion AccuVote TSx machine in its vote centers. Otherwise, the state conducts voting by mail.

Two counties in California will use the paperless AccuVote machines with printer attachments, but only for voters with disabilities.

Less secure

Security experts are also concerned about a type of electronic voting machine known as a “ballot-marking device,” which lets voters select their choices on a touchscreen before printing out a paper slip that serves as the official ballot.

These devices have surged in popularity in recent years, as local election officials scramble to replace their old paperless machines without eliminating the convenience of a touchscreen interface. But they have also prompted warnings from security experts and election-integrity activists, who say they could be vulnerable to attacks or malfunctions that cause the printed ballot to differ from the voters' selections. (Most voters don't check these ballots, studies have found.)

Some ballot-marking devices print ballots with scannable barcodes. If voters don’t check the text on those ballots before they’re scanned, and hackers have manipulated the data embedded in the barcodes, the inconsistencies will delay the reporting of correct results.

All 14 Super Tuesday states will use these devices, but to varying degrees. In some states, such as Alabama, only voters with disabilities will use these electronic voting machines. In others, such as North Carolina and Texas, certain counties will rely only on these devices.

One ballot-marking device that has drawn significant scrutiny is the Dominion ImageCast Evolution, which will appear in some polling places in Minnesota, Tennessee and Virginia. (Unlike Tennessee, Minnesota is a predominantly paper-based state. In Virginia, which has upgraded much of its election equipment since 2016, most voters will rely on hand-marked paper ballots.)

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Some security experts consider this Dominion machine riskier than other ballot-marking devices because it integrates a ballot scanner that tallies the results. The problem: Hackers who compromise the ImageCast could make it add votes to the printed ballots after voters cast them but before they're scanned.

“If the cheating software can mark my ballot, after the last time I can inspect it, then the ballot seen by the recount team is not the same as I marked it,” said Princeton University computer science professor Andrew Appel.

Paper: The safest option

Super Tuesday's most-secure swath of states will be those where the vast majority of voters hand-mark their paper ballots, while voters with accessibility issues will primarily use ballot-marking devices that experts believe have the fewest security concerns.

Those include: Alabama, Colorado (a vote-by-mail state that maintains some in-person vote centers), Maine, Massachusetts, Minnesota, Vermont and Virginia.

A wild card

California predominantly relies on hand-marked paper ballots, but many voters in Los Angeles County will use a new type of voting machine that raised objections from some security experts — and which the state approved only after imposing an unusual array of security requirements to address "critical flaws" and other shortcomings.

Some security experts and election integrity advocates have also criticized the county’s decision to award the "Voting Solutions for All People" contract to a vendor called Smartmatic, which was the subject of a congressionally requested inquiry 14 years ago into its potential foreign ties.

Los Angeles County developed the system part of the county's VSAP project, which is meant to enhance security by providing a paper-based device with software that the county owns and controls.

The state is requiring polling places in the county to have paper ballots on hand for voters who don’t want to use the VSAP system. An estimated 63 percent of the county’s voters have requested absentee paper ballots to vote by mail.