Presidential hopeful Bernie Sanders called for a constitutional amendment to automatically register all eligible voters during a Democratic candidate forum on Friday night.

He said he wanted to see legislative reform or “maybe even a constitutional amendment that says that everybody in America who has 18 years of age or older is registered to vote, end of discussion.”

Sanders blasted politicians who pass laws making it harder for people to register to vote. States across the country have passed new laws—most pushed by Republicans—that require a photo ID to register to vote or limit when people can register.

“People who suppress the vote are political cowards and are undermining democracy,” Sanders told moderator and MSNBC host Rachel Maddow during the forum at Winthrop University in Rock Hill, South Carolina.

“What the Republicans are doing is so un-American, it’s outrageous, it is beyond belief,” he said. “If they can’t face a free election, they should get another job.”

In his many elections, Sanders said, “it has never occurred to me as a candidate to figure out the way to deny people the right to vote because they might vote against me.”

Sanders expanded on his proposal in a brief post-debate interview with MSNBC host Chris Matthews.

“Its not a new idea,” he said. “Other countries around the world are doing it.” The recent election in Canada was one example of how the proposal could work, he suggested.

“Amazingly enough we do not have in our Constituion the right to vote as a Constituional right, we leave it up to the states,” he said. “That’s where I get passionately upset.”