Senators from both parties are trying to bridge the gap.
Drawing on the lessons from battles in the 1980s and ’90s over the Brady Bill, which failed in Congress several times before ultimately passing, gun control supporters believe they can prevail by working on a two-pronged strategy. First, they are identifying senators who might be willing to change their votes and support a background check system with fewer loopholes.
Second, they are looking to build a national campaign that would better harness overwhelming public support for universal background checks — which many national polls put at near 90 percent approval — to pressure lawmakers.
Senators Joe Manchin III, Democrat of West Virginia, and Patrick J. Toomey, Republican of Pennsylvania, have been talking in recent days about how they could persuade more senators to support their bill to expand background checks for gun buyers, which drew backing from only four Republicans last week.