For all the abuse he’s taking, Schumer may actually be protecting the Democratic Party from the real political danger inherent in Obama’s actions. The contempt that the president and John Kerry showed by taking this agreement to the UN before submitting it to Congress and the American people was reckless. They are not only thumbing their noses at the American people and Congress, but they are showing contempt for the primacy of our system of checks and balances and they could be setting up the Democratic party for years of attacks of “you caused this!” every time Iran behaves in a threatening manner. 

Should Obama veto a bill blocking the Iran deal and defy the will of Congress, he would once again find himself on the wrong side of public opinion: 61 percent of voters would want a veto overridden. If a veto is sustained solely by Democrats two-thirds of respondents, including a plurality of Democrats say they would blame the Democratic party if Iran got a nuclear weapon or used the money from sanction relief to support terrorist attacks on Israel.

By contrast, Schumer’s principled stand enjoys broad support: In another part of the SAN poll, Democratic voters were asked what their senators and representatives should do when faced with difficult choices—support the president or follow their conscience if they oppose him—35 percent said that they should “trust the President and his negotiators and support their party’s leader,” while 59 percent wanted their representatives and senators to set aside party loyalties and follow their conscience on the issue at hand.