Which gun control measures are gaining momentum in Congress?

Bipartisan support is evident for universal background checks, stricter laws against gun trafficking, and limits on high-capacity magazines. But consensus in the GOP-controlled House will depend on what the Senate accomplishes.

Are specific gun-control measures beginning to build momentum in Congress? Key lawmakers in recent comments have indicated that’s the case. For instance, Sen. John McCain (R) of Arizona on Sunday said many senators are lining up behind a bipartisan plan whose centerpiece is an expansion of background checks on gun purchasers.

“I think that most of us will be able to support” that package, said Senator McCain on NBC’s "Meet the Press."

Background checks have long been seen as a sweet spot in the gun debate that could draw both Republican and Democratic votes, but McCain’s tacit endorsement is still a “key moment,” writes liberal-leaning Greg Sargent in his Plum Line Washington Post blog.

The bipartisan group that’s pulling the plan together includes Sen. Joe Manchin of West Virginia, a key pro-gun Democrat, and conservative GOP Sen. Tom Coburn of Oklahoma, Mr. Sargent notes. It would include expanded sharing of data on mental illness and likely have some sort of provision ensuring that the checks don’t lead to a national registry of gun owners.

“Having Coburn and Manchin bless such a proposal would give it a major boost, even among GOP lawmakers inclined to robotically do whatever the NRA [National Rifle Association] tells them to do,” he writes.

This doesn’t mean the plan is tied up with ribbon and a bow; another member of the bipartisan effort, Sen. Chuck Schumer (D) of New York, added on Sunday that the group has made good progress but still has some hard issues to resolve.

“Guns [are] a very difficult issue,” said Senator Schumer on CNN’s "State of the Union."

Asked whether a ban on assault weapons would be included in the Senate’s package, Schumer side-stepped the issue. He noted that Sen. Dianne Feinstein (D) of California has introduced legislation to prohibit such military-style firearms and said that her bill will get a vote on the Senate floor.

“Whether it’s part of our bill, we’ve been focusing on universal background checks, where I think there’s a greater chance to come to a bipartisan agreement,” said Schumer.

(Currently, federal law requires background checks only for customers of federally licensed firearm dealers. They aren’t required for private transactions, many of which occur at gun shows. Some states have more stringent check requirements of their own.)

Another gun provision the Senate might be able to pass is a new federal law against firearms trafficking. In essence, this would give prosecutors another way to go after those who legally purchase guns and then pass them to others who use them to commit crimes.

It’s also possible the Senate will at least seriously consider proposals to ban high-capacity ammunition magazines, as well. Sen. Frank Lautenberg (D) of New Jersey has introduced legislation that would ban any magazine that holds more than 10 rounds.

“There is no place in our communities for military-style supersized magazines like those used inside Sandy Hook Elementary School, in Aurora, and in Tucson,” said Senator Lautenberg last month when he introduced the bill.

It’s important to remember that the Senate is but the first hurdle for any new gun curbs. They’d have to pass the GOP-controlled House, as well, where it’s less clear there’s any consensus for new measures.

Senate Judiciary Committee Chairman Patrick Leahy (D) of Vermont, a key player in the issue on the Senate side, said over the weekend that it is his understanding that the House will just wait to see what the Senate does, and then decide upon its plan of action.

“They feel if we’re able to do something there might be a chance. If we’re unable, frankly, they’re not going to try anything at all. I think that’s a political reality,” Senator Leahy told NPR's "Weekend Edition" on Saturday.