Stephen Gutowski of the Washington Free Beacon documents Sen. Bernie Sanders’ wavering support for — and eventual rejection of — key gun-rights arguments.

Bernie Sanders has campaigned on his reputation as an outsider to become the Democratic presidential frontrunner, but the independent Vermont senator, who long took moderate positions on gun control, is now fully embracing left-wing positions on the issue as he works to become the Democratic Party’s standard bearer in 2020.

Sanders long reflected the sensibilities of the rural gun culture of low-crime Vermont, even as the Democratic Party embraced increasingly restrictive gun control. He voted against a law establishing gun dealer licensing and background checks while supporting a law protecting gun dealers and manufacturers against frivolous lawsuits. For much of his career, he defended Vermont’s gun culture and said that he hoped to bridge the gap between his constituents and high gun-crime cities such as Chicago and Los Angeles.

No longer. Political experts say that Sanders has moved to the left along with the rest of his party after he issue became a major vulnerability for him in his 2016 primary campaign against Hillary Clinton, who found and exploited Sanders’ rare vulnerability on the left.

“Bernie shifted with the Democratic Party (even as an independent),” Professor Larry Sabato, director of the University of Virginia Center for Politics, said in an email. “And he saw in 2016 his gun record could be a real detriment to his presidential ambitions.”