WASHINGTON (AP) -- The Senate set a long-awaited vote for Wednesday on a bipartisan plan for expanding background checks to more firearms buyers, with supporters facing a steeply uphill path to victory.
By scheduling the roll call, Senate leaders ensured a showdown over the cornerstone of an effort by gun control supporters to tighten firearms laws following December's killings of 20 students and six aides at an elementary school in Newtown, Conn.
The Senate planned to vote on eight other amendments as well to a Democratic gun control bill that besides expanding background checks, would tighten laws against gun trafficking and boost school safety aid.
They included Democratic proposals to ban assault weapons and high-capacity ammunition clips, which are expected to lose; a Republican proposal requiring states to honor other states' permits allowing concealed weapons, which faces a close vote; and a broad GOP substitute for the overall gun measure.
The focus of both sides has been on a compromise by Sens. Joe Manchin, D-W.Va., and Patrick Toomey, R-Pa., broadening background checks. It will be the first amendment voted on Wednesday. Despite appearances at the Capitol on Wednesday by wounded former Rep. Gabrielle Giffords, proponents seem to face enough potential opponents to derail their endeavor unless they can figure out how to win more votes.
No. 2 Democratic leader Richard Durbin of Illinois, his party's chief vote counter, left a lunch of Democratic senators saying they would need support from nine or 10 Republicans -- a tall order.
Attending Tuesday's Senate lunch was Giffords, the Arizona Democrat severely hurt in a 2011 mass shooting in Tucson, and her husband, retired astronaut Mark Kelly. The two, gun owners both, have started a political committee that backs candidates who favor gun restrictions.
"His message was, 'We've been through this,'" Durbin said, describing Kelly's remarks to the lawmakers. "'We're ready to fight back to stand up for those who have the courage to vote for gun safety.'"
Giffords did not address the lawmakers.
In a blow to gun control advocates, Sen. Dean Heller, R-Nev., became the latest Republican to say he will oppose a bipartisan compromise broadening background checks.
"I believe that this legislation could lead to the creation of a national gun registry and puts additional burdens on law-abiding citizens," he said.
Before the lunch, Giffords and Kelly met privately with Manchin and Toomey. Their compromise would expand background checks to cover gun shows and the Internet, a plan gun control supporters think gives them the best chance of pushing a broader system of checks through the Senate.
"They're helping immensely just by being here and talking to our colleagues. We're close, but we sure need their help," Manchin said after that meeting.
Manchin and Toomey were no longer considering a change to their bill to exempt people who live far from gun dealers, making it difficult to go to the dealers' shops to have background checks performed. The hope had been to attract votes from Alaska and North Dakota senators, and the sponsors' decision to move ahead without it seemed to suggest that the effort to win over those senators would fail.
Background checks are aimed at weeding out criminals and the seriously mentally ill from getting firearms. The current background check system applies only to transactions with licensed gun dealers.
President Barack Obama, in an interview with NBC's "Today" show, urged lawmakers to pay attention to public support for expanding background checks and remember the massacre at Sandy Hook Elementary School.
"The notion that Congress would defy the overwhelming instinct of the American people after what we saw happen in Newtown, I think is unimaginable," Obama said in the interview, aired Tuesday.
National Rifle Association spokesman Andrew Arulanandam said the organization was spending $500,000 on an online video ad on conservative and Washington-area websites that cites a survey from a police-oriented website showing opposition to gun control proposals. "Tell your senator to listen to America's police, instead of listening to Obama and Bloomberg," said the ad, referring to gun control advocate Michael Bloomberg, New York City mayor.
While all states but Illinois, plus the District of Columbia, issue permits or have other arrangements for permitting concealed weapons, nine states don't recognize permits from other states. Gun rights defenders say making it easier to move firearms between states is protected by the Constitution, while opponents complain it would hurt states that have stricter standards for permits than others.
The amendment requiring states to recognize concealed weapons permits from elsewhere was being sponsored by Sen. John Cornyn of Texas, the No. 2 Senate GOP leader.