Controversial gun legislation cleared a key Senate hurdle Thursday, as lawmakers voted 68-31 to start debate on the package which includes expanded background checks and new penalties for gun trafficking.

Senate Democrats, joined by 16 Republicans, were able to overcome an attempted filibuster by GOP senators opposed to the current bill. Those senators could still slow-walk the debate, but the Senate will eventually begin votes on amendments — one of which is considered crucial to winning support for a final vote.

Though the bill cleared a 60-vote hurdle on Thursday, supporters will likely have to corral another 60-vote majority when it comes time to call a final vote, which Democrats acknowledged is a heavy lift.