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For many, Trump's decision on Tuesday to pull out of the landmark nuclear deal marked the final death knell for the hope created when it was signed in 2015 that Iran might finally escape decades of isolation and US hostility. (Photo by ATTA KENARE / AFP)        (Photo credit should read ATTA KENARE/AFP/Getty Images)
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Story highlights

56% of Americans want Congress to reject the Iran deal, according to the latest CNN/ORC poll

This comes as Americans are increasingly divided over the deal along partisan lines

Washington CNN —  

A growing majority of Americans are turning against the nuclear deal with Iran and believe Congress should reject the deal brokered between the U.S., five other world powers and Iran.

As Congress inches closer to a vote to approve or disapprove of the deal, 56% of Americans now say they think Congress should reject the deal with Iran – up from 52% less than a month ago – according to the latest CNN/ORC poll released Thursday.

And 6-in-10 Americans also disapprove of President Barack Obama’s handling of the U.S. relationship with Iran, according to the poll.

The American public’s growing disapproval of the Iran deal stems from an increasing partisan polarization over the deal with more Republicans opposing and more Democrats embracing the nuclear deal. And it comes amid a full-court press from Obama and his administration to sell the deal to the public and to members of Congress ahead of a key vote on the deal next month – with Republicans knocking his efforts at every turn.

READ: The complete CNN/ORC poll results

Republican opposition has jumped to 83% from 66% last month while 70% of Democrats now say Congress should approve the deal, up from 61% in July.

The number of independents opposing the deal, meanwhile, remains steady as a majority – now 58% – continues to believe Congress should reject the deal.

Republican politicians have been nearly unanimous in their opposition to the deal with most of the party’s presidential field expressing outrage and opposition to the deal almost as soon as it was announced.

And with Democratic frontrunner Hillary Clinton expressing her support for the deal, it is likely to become a defining issue in the 2016 election.

A slice of the opposition to the deal may be drawn from the partisan politics behind it as half of the American surveyed said they supported a deal that would ease some economic sanctions against Iran in exchange for major restrictions on Iran’s nuclear program and greater international inspections of its nuclear sites – essentially the terms agreed to by Iran and six world powers.

With nearly all Republicans committed to opposing the deal when it comes up for a vote next month, Obama will likely have to pull out his veto pen to keep the deal alive.

Two leading Senate Democrats – Sen. Charles Schumer of New York and Sen. Bob Menendez of New Jersey – have already announced their opposition to the deal and vowed to vote to override Obama’s veto if necessary.

But unless another 11 Senate Democrats join that bandwagon, opponents of the deal won’t have the votes to keep the agreement from going into effect.