Days after the Orlando massacre, U.S. Sen. Edward Markey of Massachusetts joined Sen. Elizabeth Warren and other Democrats in holding a 15-hour filibuster advocating for new gun laws.
"I think everything changed in Orlando," Markey said. "We are in a new era."
The senators are hoping to pass a measure that would ban anyone on the no-fly list or terrorist watch list from buying assault weapons — it would also require background checks on all purchases.
"It's time for us to have a showdown on the floor of the floor of the Senate," Markey said.
Democrats say they are common sense measures, but gun rights advocates say there are civil rights issues.
"What's the due process? If you're suddenly put on a list, who makes that decision? What's the criteria for that decision?" asked Jim Wallace of the Massachusetts Gun Owners Action League.
The gunman in the Orlando massacre was not on a terrorist watch list when he opened fire with a semi-automatic rifle and a pistol, killing 49 people — he was on the list for 10 months, then removed.
He purchased the weapons legally.
"Tell us how you are going to handle the huge mental health problem in this country and how you're going to handle terrorists on U.S. soil. Because those are the two main issues with all of the mass murders," Wallace said.
But Republicans who have vocally opposed gun control laws are opening themselves up to debate.
U.S. Sen. Kelly Ayotte of New Hampshire was called out for preventing a terror watch list ban in the past — Friday, she said she was open to discussing new measures. Republican presidential candidate Donald Trump has said that he would do the same.
Ayotte is working with Senators Susan Collins of Maine and Jeff Flake of Arizona on legislation aimed at preventing suspected terrorists from being able to purchase guns.