As with ObamaCare, the polls now show more than half of the public is opposed to the Iran deal—despite Mr. Obama’s vigorous promotion and a cheerleading media. Also like ObamaCare, the President is assuring Democrats that public support will improve once the pact goes into effect.

But this makes Democrats hostage to Iran’s behavior. This means hostage to Supreme Leader Ayatollah Ali Khamenei, who recently said that “even after this deal our policy toward the arrogant U.S. will not change.”

It means hostage to Mohammad Yazdi, head of Iran’s powerful Assembly of Experts, who declared this week that “we should not change our foreign policy of opposition to America, our number one enemy, whose crimes are uncountable.” Ayatollah Yazdi will play a large role in selecting Ayatollah Khamenei’s successor.

And it means hostage to Qasem Soleimani, head of the Quds Force of Iran’s Revolutionary Guard Corps, which will receive billions of dollars in cash once sanctions are lifted. Mr. Soleimani is likely to deploy that cash to fund terrorism and proxies fighting in Iraq, Syria, Lebanon, Yemen and Gaza. Democrats will have essentially voted to finance Iran’s combination of Persian imperialism and Shiite messianism.