Did Republican senators really think Iranian leaders needed a primer on how the U.S. government works? The open letter they sent to the leaders of Iran Monday was an unnecessary partisan stunt that detracts from what matters most.

That is, any deal with Iran must include a requirement for unannounced inspections of its nuclear facilities. Verification must be pervasive and intrusive enough to give the world confidence that if Iran cheats, it will be caught before it can produce a bomb.

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After all, President Barack Obama's critics say they want the same thing he does -- to ensure that Iran, a sponsor of terrorism and a threat to Israel, doesn't become a nuclear power.

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Unfortunately the partisan static over negotiations to curtail Iran's nuclear weapons program became unnecessarily louder this week.

Senate Republicans doubled down on House Speaker John Boehner's invitation to Israeli Prime Minister Benjamin Netanyahu to address a joint session of Congress last week. Netanyahu used the platform to insist Obama was about to strike a bad deal that would pave the way for Iran to become a nuclear power.

The letter, signed by 47 of 54 Senate Republicans, told Iran that unless Congress approved it, any nuclear deal with Obama could expire the day he walks out of the Oval Office -- claiming in effect that they are the key players, not the president of the United States. In addition to flexing for their political base, the senators may be gambling that their intransigence will result in a better deal.

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The risk, however, is sabotaging the multination negotiations and leaving Iran unrestrained in building nuclear weapons. That's a bad path that could lead to use of military force to stop Iran's pursuit of a bomb.