Emanuel, who led the Democrats’ successful effort to retake the House in 2006, gained an appreciation for how skittish critical swing state members were on the gun issue and steered clear of the matter. When he joined the Obama White House as chief of staff, he blew a gasket, according to an account in the book “Kill or Capture,” when Attorney General Eric H. Holder Jr. suggested the administration would push to reinstate the assault-weapons ban. (Emanuel’s office said the mayor had a 20-year record of standing up to the National Rifle Association and fighting to get assault weapons off America’s streets.)

And Schumer, the great champion of the assault weapons ban in the House, become remarkably less vocal about it after winning election to the Senate and eventually leading his party to a majority in that chamber. (Schumer’s office insisted that the senator has picked his spots, whipping up votes against a bill that would have gutted laws criminalizing concealed weapons, fending off NRA-backed bills that would have made it easier for mentally ill veterans to get guns and authoring a gun-control measure that strengthened background checks after the 2007 Virginia Tech shooting.)

Yassky acknowledged that the NRA exercised real political muscle through its ability to trigger a flood of member phone calls to targeted congressmen who supported gun control measures. And, he adds, some elected officials did lose their seats in part because of the passage of the assault weapons ban, most notably Brooks, who sponsored the larger bill but opposed the ban. But he pointed out that plenty of members from pro-gun districts who supported the ban survived and that gun control was a popular issue for no less a political animal than Clinton to run ads in support of the issue in his 1996 reelection victory against Sen. Robert J. Dole. In 2000, Yassky helped write the gun-control portion of Al Gore’s platform, which called for a national gun license and registration framework — akin to driver’s license and registration.