Determined foes of President Obama's nuclear deal with Iran had vowed to use August to fire up public opposition and to build a bipartisan majority in Congress to sink the landmark pact.
Instead, the effort fizzled. The result gave a boost to a White House that has often had rocky relations with even fellow Democrats on Capitol Hill and an unaccustomed defeat to Washington's pro-Israel lobbying groups, which are often regarded as among the Capitol's most effective interest groups.
The deal's survival was in effect sealed Wednesday when Barbara Mikulski (D-Md.) gave the White House a crucial 34th Senate backer. That's enough to ensure that even if Congress passes a resolution to disapprove the agreement, Obama would have sufficient votes to uphold a veto.
With that victory in hand, Obama's Senate allies will try to nail down the votes of seven of the final 10 Democrats who have yet to declare a position. If they succeed, they could block a floor vote on the disapproval resolution this month so Obama wouldn't need a veto to protect what his aides view as the most significant diplomatic deal in decades.
Several factors led to the opposition's failure.
Opponents of the deal may have miscalculated the degree of public interest in the debate. They hoped for the kind of outpouring of public anger that gave rise to the tea party and nearly doomed Obamacare in August 2010.
But the Iran deal "just hasn't had that kind of galvanizing effect" on the public, said Rep. David Price (D-N.C.), who backs the agreement.
Polls suggest that although some Americans are passionate about the deal, most feel more ambivalent than energized. White House warnings that congressional rejection of the pact could lead to war have also resonated with the public.
Moreover, a Republican invitation to Israeli Prime Minister Benjamin Netanyahu to address both houses of Congress in March appears to have backfired. His harsh denunciation of the negotiations then underway, which the White House portrayed as a snub of Obama's foreign policy, made the debate more polarizing and partisan, pushing Democrats to the president's side.
Another factor, said one frustrated Republican on Capitol Hill: "Trump happened."
The GOP leadership aide, granted anonymity to discuss the setback, said billionaire Donald Trump's attention-grabbing presidential campaign, along with scrutiny of Hillary Rodham Clinton's email server, overshadowed all other issues this summer, making it harder for the Republicans' message to attract attention.
Cliff Kupchan, an Iran specialist and chairman of the Eurasia Group risk advisory consulting firm, said the deal "turned out to be good enough" to survive the political market.
"The administration was effective in raising the question: 'What's the alternative?'" Kupchan said. "They beat back the arguments that pushing for an extension of sanctions on Iran would produce a better deal."
The agreement between Iran and six world powers — the United States, Britain, France, Russia, China and Germany — will ease international economic sanctions on Iran in exchange for limits on its ability to enrich uranium and conduct other nuclear activities for at least 15 years.
Among the losers in the political arena is the American Israel Public Affairs Committee. Known as AIPAC, the powerful pro-Israel lobby helped raise tens of millions of dollars for an advertising campaign intended to sway public opinion — and wavering Democrats — to oppose the deal.
AIPAC instead is facing a rare political defeat — arguably its most significant since the Reagan administration in the early 1980s — and has damaged its image as the leading bipartisan voice for Americans who strongly support Israel.
"We're certainly not at the place the opponents of this agreement projected us to be," said Victoria Kaplan, who led a pro-deal campaign for the advocacy group MoveOn.org.
In a letter to her colleagues Wednesday, House Minority Leader Nancy Pelosi (D-San Francisco) also vowed veto-proof support in that chamber. "I am confident we will sustain the president's veto in both houses of Congress," she said.
Democrats have felt free to back the deal in part because they heard from many in the American Jewish community who split from the more hawkish AIPAC.
The dozen or so Democratic opponents in Congress come mainly from parts of New York, New Jersey and Florida with large politically conservative Jewish populations. But the opponents failed to mount a serious effort to persuade other lawmakers to buck the White House.
The most important Democratic defector, Sen. Charles E. Schumer of New York, is poised to become the next party leader, but he publicly declined to pressure colleagues to join him. Only one other Democratic senator, Robert Menendez of New Jersey, has lined up with Schumer, although others may yet join their ranks.
Whereas some Democrats quickly lined up behind the president, others have claimed to be deeply conflicted and may not issue their decisions until the vote, which is expected by Sept. 17, the self-imposed deadline for congressional review. Some have written lengthy explanations and delivered their decisions in solemn speeches.
Mikulski, who will retire after next year as the longest-serving woman in Congress, called the vote "among the most serious" of her career.
Both sides launched intense lobbying campaigns. The administration organized classified briefings, and Obama phoned or met numerous House and Senate members, or wrote personal letters to them. He reached across the aisle at times, inviting Sen. Jeff Flake (R-Ariz) aboard Air Force One on a recent trip to Africa in hopes of winning his support. Flake ultimately opposed the deal, and no Republicans are likely to back it.
Disappointed opponents insist the White House is enjoying what the GOP leadership aide called a "high-water mark" for a flawed deal.
Opponents and several Republican presidential candidates vow to dismantle the deal in the future, much as foes promised to repeal and replace Obamacare.
Far from conceding defeat, AIPAC spokesman Marshall Wittmann said that a bipartisan majority in Congress still opposes the deal, and that no major arms control agreement has been approved by only a minority.
Speaking to reporters traveling with Obama in Alaska, White House Press Secretary Josh Earnest took a more optimistic view.
"The administration is encouraged that more than a third of the United States Senate has now indicated that they'll support the successful implementation of the international diplomatic agreement to prevent Iran from obtaining a nuclear weapon," he said. "This strong support is a validation of the outreach that the president and his team have organized to make sure that every member of the Senate understands exactly what's included in this agreement."
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