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Washington • The White House aggressively struck back after Sen. Charles Schumer announced his opposition Thursday to President Barack Obama's Iran nuclear deal, suggesting the New York Democrat could lose support as party leader in the Senate in 2016 if he helps block the accord.

The forceful response was the latest example of the president's take-no-prisoners approach to ensuring the survival of a pact he views as a legacy-defining achievement that could help remake the security situation in the turbulent Middle East.

The White House and its allies expressed confidence that Schumer's opposition would not be enough to derail the Iran deal. Senate Democratic aides said 14 members of the caucus have expressed support, and Schumer is the only one to publicly oppose it.

But both sides acknowledged that the debate is now headed into a period of uncertainty as Obama is vacationing for two weeks in Martha's Vineyard and Congress is breaking for its six-week summer recess. As lawmakers head home to their districts, some are expected to be confronted by constituents who oppose the deal. Several influential Jewish American groups have launched multimillion-dollar advertising campaigns against it.

Although Schumer indicated that he would not actively encourage others to vote against the Iran deal, the White House moved to marginalize his position, citing his support for the Iraq war in 2003 as part of a longstanding tendency to disagree with Obama on foreign policy and the use of U.S. power.

White House Press Secretary Josh Earnest dismissed Schumer's stance, saying that it is "not particularly surprising to anybody here at the White House, even if it was disappointing." Schumer's position "doesn't change our confidence that we'll be able to mobilize a substantial majority of Democrats," Earnest said but suggested lawmakers should question whether Schumer is fit to become the party's leader in the Senate next term, saying members may want to "consider the voting record of those who want to lead the caucus."

Close White House allies made similar arguments.

"Senator Schumer siding with the GOP against Obama, Hillary Rodham Clinton and most Democrats will make it hard for him to lead the Dems in '16," Dan Pfeiffer, who served as Obama's senior political adviser until leaving in February, wrote on Twitter. "The base won't support a leader who thought Obamacare was a mistake and wants war with Iran."

Schumer has previously criticized the timing of passing Obama's Affordable Care Act as a political mistake. Despite the White House reaction, Schumer maintains broad support among his colleagues, and there is no indication that his expected ascension to Senate Minority leader is in jeopardy.

Schumer, who is Jewish, said he would not support the agreement out of concern that it will only strengthen Iran by boosting its economy and ultimately may not prevent the country from developing a nuclear bomb.

Obama has pledged to veto any bill rejecting the accord, which would lift economic sanctions against Iran and require the country to dismantle much of its nuclear infrastructure. He has bluntly confronted his opponents, including Republicans, Jewish-American leaders and Israeli Prime Minister Benjamin Netanyahu, stating that they would prefer war over a diplomatic solution to containing Iran's nuclear ambitions.

Obama has also launched a publicity blitz that included a major speech at American University, a private two-hour session at the White House with two dozen Jewish-American leaders, an on-the-record chat with nine foreign-policy columnists and will culminate with an interview with CNN's Fareed Zakaria that will air Sunday.