One of the most fascinating political-science experiments in recent years was conducted in 2013 by two of the most-respected pollsters in the business, Democrat Mark Mellman and Republican Whit Ayres. They presented two groups of respondents with two different education proposals, labeling one as the Republican plan and another as the Democratic plan. To the second group, they reversed the partisan labels for the plans, but described them in exactly the same way. The results were striking: When Plan A was presented as the Democratic plan, 75 percent of Democrats backed it. When the exact same plan was labeled as the Republican plan, only 12 percent of Democrats supported it. As Mellman concluded, "Policy positions were not driving partisanship, but rather partisanship was driving policy positions."
That maxim is being put to the test on the issue of President Obama's Iranian nuclear deal, which is forcing Democratic Party officials with a history of supporting Israel to choose between loyalty to their president against voter sentiment back home.
From a political perspective, the vote will be a telling test of Mellman and Ayres's thesis. Support for Israel is overwhelming in the United States, with a long history of bipartisan backing (though support among Democrats has frayed in recent years). A February Pew Research poll found 77 percent of respondents saying U.S support for Israel was "about right" or "not supportive enough." Only 18 percent disagreed.