Still, the politics of the issue will be tough, with Republicans and Democrats from rural states reluctant to challenge the gun lobby. The bill passed the Judiciary Committee by a party-line vote last week, and Senate Democratic aides are skeptical it will earn 60 votes on the Senate floor.

Nevertheless, Democrats hope that they can wrangle enough support. President Obama made new gun control measures a priority of his second term after last year's Newtown, Conn., elementary school shooting that left 20 children and six adults dead.

Senate Majority Leader Harry ReidHarry Mason ReidAmendments fuel resentments within Senate GOP Donald Trump is delivering on his promises and voters are noticing Danny Tarkanian wins Nevada GOP congressional primary MORE (D-Nev.) said Thursday that a new firearms bill needed to expand background checks.

“I want to be clear: In order to be effective, any bill that passes the Senate must include background checks,” he said.

Alexander Bolton contributed to this report.