Reporting from Washington — A new arms reduction treaty between the United States and Russia seemed headed for certain Senate ratification after Republican opposition crumbled Tuesday beneath a torrid campaign of White House pressure.
Eleven Republican senators joined Democrats in cutting off debate over the treaty, and more could join when the Senate votes on the treaty Wednesday, giving the White House a major foreign policy victory.
The Republican support for the agreement, known as the New START treaty, came in defiance of GOP leaders, who opposed ratification but did not insist that everyone remain in lock step on the issue.
That freed a few moderate Republicans to abandon Minority Leader Mitch McConnell and join the party's respected foreign policy statesman, Sen. Richard G. Lugar of Indiana, in support of the treaty.
Underscoring the schism among Republicans, the party's No. 3 leader, Sen. Lamar Alexander of Tennessee, announced his support for the treaty, saying it would make Americans safer and more secure. Other Republicans followed suit.
"We know when we've been beaten," Sen. Orrin G. Hatch (R- Utah) said before the procedural vote to cut off debate. He voted no.
The treaty calls for reducing the maximum number of long-range nuclear warheads in each nation from 2,200 to 1,550 within seven years of ratification. It limits to 700 the number of launchers each country maintains to deliver the nuclear weapons, and sets out procedures for verification of compliance.
President Obama has described completion of the treaty, which he and Russian President Dmitry Medvedev signed in April, as imperative to national security.
The administration exerted pressure on senators by assembling a phalanx of national security officials from four decades of Republican and Democratic administrations to support the treaty, including former Republican Secretaries of State Henry A. Kissinger, James A. Baker III, Colin L. Powell and Condoleezza Rice, as well as former President George H.W. Bush.
The effort intensified in recent days, with Obama, Vice President Joe Biden and Secretary of State Hillary Rodham Clinton lobbying senators. Obama also issued promises to seek billions of dollars to modernize the nation's nuclear arsenal and follow through on U.S. missile defense programs abroad, a potential source of jobs at home.
White House staffers set up operations in a Capitol office to better respond to questions and address concerns about the treaty, a full-court press rare for the Obama administration but welcomed by Democratic congressional leaders.
"We are on the brink of writing the next chapter in the 40-year history of wrestling with the threat of nuclear weapons," Sen. John F. Kerry (D-Mass.), chairman of the Senate Foreign Relations Committee, said after the 67-28 vote.
Adoption of the treaty in the lame-duck congressional session would be another bipartisan victory for Obama, who had appeared politically hobbled after his party's drubbing in last month's midterm elections. Congress has passed a White House-supported package of tax cuts and unemployment benefits, and legislation to allow gays to serve openly in the military.
The New START treaty confronted Senate Republicans with a painful split in their leadership, between Lugar and the party's No. 2 leader, Sen. Jon Kyl of Arizona, the GOP whip who was a critic of the treaty and opposed bringing it up for a vote during the end-of-year session.
McConnell publicly sided with Kyl, but did not use his political capital to force Republican colleagues to desert Lugar.
Although McConnell had kept the GOP together in opposing a massive government funding bill, it had become increasingly clear that halting the nuclear pact appealed to a narrow slice of the population, mainly those on the conservative right.
Lugar began with support from moderate Sens. Susan Collins and Olympia J. Snowe of Maine and George V. Voinovich of Ohio. On Monday, Sen. Scott Brown of Massachusetts declared his support.
After Alexander's announcement of support Tuesday, Bob Corker of Tennessee, Lisa Murkowski of Alaska and Johnny Isakson of Georgia also said they would back ratification.
All of those senators, along with Thad Cochran of Mississippi and Robert F. Bennett of Utah, voted to cut off debate.
Other Republicans, including Judd Gregg of New Hampshire, may vote in favor of ratification.
Despite the growing GOP support, administration officials are taking few chances, remembering that McConnell last week was able to void Republican support for the omnibus government funding package. That package was important to the White House because it contained funding for the administration's healthcare and financial regulation initiatives.