ONE UNSETTLING result of the debate over gun violence has been a spike in firearm purchases. New figures released by the FBI suggest that Americans bought firearms in record numbers in November, December and January. Although it is not a precise one-to-one indicator of purchases, the FBI performed more than 2.7 million firearm background checks in December and more than 2.4 million in January; in November the total was more than 2 million. All three months were the highest since the agency began keeping records in 1998.

The frenzy of gun purchasing may reflect anticipation of new gun-control legislation, and those bets are well founded. Public pressure for action is still running strong in the aftermath of the Dec. 14 massacre at Sandy Hook Elementary School in Newtown, Conn. Bills are being drafted on Capitol Hill. President Obama and Vice President Biden have kept the issue on the front burner. The gun lobby is trying frantically to throw up obstacles, but the prospects are promising for new legislation.

Now the question becomes: What should be done, and what can be done, given the politics? We’ve advocated a ban on semiautomatic assault rifles, military-style weapons that have no place on our streets. This is the goal of legislation introduced by Sen. Dianne Feinstein (D-Calif.) that would prohibit the sale and manufacture of 157 types of semiautomatic weapons in an effort to “dry up the supply,” as the senator put it. The president has also endorsed such a ban; the last one expired in 2004. But politically, this is the most difficult bridge to cross, and there are real doubts about whether sufficient votes exist for it in Congress.

Public opinion surveys show overwhelming support, even among gun owners, for measures to require universal background checks for gun purchases, and this ought to be the backbone of bills to be brought before the House and Senate. Last week Rep. Eric Cantor (R-Va.), the House majority leader, suggested modeling a federal check system on the one developed in his state after the 2007 shootings at Virginia Tech. At hearings recently before the Senate Judiciary Committee, Baltimore County Police Chief James Johnson, speaking on behalf of the National Law Enforcement Partnership to Prevent Gun Violence, noted that 40 percent of gun sales are not subjected to background checks, which he compared to “allowing 40 percent of passengers to board a plane without going through security.”

A second goal with wide support is to pass stricter laws against gun trafficking, which also should be considered promptly by Congress.

It will prove somewhat more difficult to enact a ban on high-capacity magazines like those used in recent mass murders, but not impossible. Ms. Feinstein’s bill would prohibit magazines holding more than 10 bullets, a worthy goal, keeping in mind that clips with 30 bullets have been used to mow down people at schools, theaters and shopping centers. At the Senate hearing, former representative Gabrielle Giffords, gravely wounded in the 2011 Tucson shooting, appealed to Congress: “We must do something. The time is now. You must act.”

It is a miracle that Ms. Giffords could say those words. Congress should heed them.