Super Tuesday brings a supersized election security challenge

Millions of voters across the country will cast ballots during Super Tuesday on old, insecure election equipment — even after nearly four years of handwringing and warnings about Russian election interference.

The jurisdictions at risk include three of Tennessee’s biggest counties — Shelby, Knox and Rutherford — where the paperless voting machines at the polls will include devices with security flaws so alarming that voters tried suing to have the equipment removed from precincts. Dozens of small counties in Texas are also sticking with risky touchscreen machines that have no paper trail to help detect tampering or malfunctions. And in California, Los Angeles County is debuting new voting machines that have drawn scrutiny for security weaknesses, as well as their developer's past alleged ties to the Venezuelan government.

The news is better in other parts of the Super Tuesday map, as some counties and states have successfully replaced their old paperless voting equipment with more secure paper-based machines. But even some of this new technology presents vulnerabilities that hackers could exploit to tamper with the primaries.

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: