Israel has become a deeply partisan issue for ordinary Americans as well as for politicians in Washington, a shift that may represent a watershed moment in foreign policy and carry implications for domestic politics after decades of general bipartisan consensus.

Republicans by a ratio of more than 2-to-1 say the United States should support Israel even when its stances diverge from American interests, a new Bloomberg Politics poll finds. Democrats, by roughly the same ratio, say the opposite is true and that the U.S. must pursue its own interests over Israel's.

Further illustrating how sharply partisan the debate has become, Republicans say they feel more sympathetic to Israeli Prime Minister Benjamin Netanyahu than to their own president, 67 percent to 16 percent, while Democrats are more sympathetic to President Barack Obama than to Israel's prime minister, 76 percent to 9 percent.

"Israel is an emotionally charged issue, period," said J. Ann Selzer, president of West Des Moines, Iowa-based Selzer & Co., which conducted the poll. "It's affecting a broader audience than the Jewish vote."

The survey also highlights how differently the nuclear negotiations with Iran are seen between Republicans and Democrats.

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Democrats, by a nearly 3-to-1 ratio, said they were more optimistic than pessimistic that a tentative deal with Iran announced this month will contain Iran's ability to get nuclear weapons and thus make the world safer.

By a 2-to-1 margin, Republicans were more pessimistic than optimistic about the impacts of a deal.

The survey of 1,008 adults, conducted April 6-8, has a margin of error of plus or minus 3.1 percentage points.