President Obama and President Hassan Rouhani of Iran have spent time trying to sell the Iran nuclear deal to skeptics among their constituents. Mr. Obama addressed pro-Israel supporters at a Washington think tank. Mr. Rouhani’s speech to a university audience in Tehran was televised nationally.
Either side could undermine the November interim agreement, and with it the best chance in 30 years for a genuine thaw in Iranian-American relations. But the more serious threat seems to be on the American side.
In the agreement, Iran committed to freezing or rolling back parts of its nuclear program and allowing daily inspections for six months, in exchange for modest sanctions relief. Meanwhile, negotiators for both sides will work toward a more lasting agreement.
While it is not perfect, the six-month hiatus is unquestionably a good deal. It would put the first meaningful curbs on Iran’s program in a decade. It certainly beats military action, which Mr. Obama holds out as an option if talks fail.
In recent days, however, reports have circulated in Washington that two members of the Senate — Robert Menendez, a New Jersey Democrat, and Mark Kirk, an Illinois Republican — are preparing legislation that would impose new sanctions on Iran’s remaining exports and strategic industries if, at the end of six months, the interim agreement goes nowhere.
Both Iran and the White House warn that such legislation could be fatal to the agreement. Mohammad Javad Zarif, Iran’s foreign minister, said that “the entire deal is dead” even if the penalties do not take effect for six months.
Similar mischief is afoot in the House. Rep. Steny Hoyer of Maryland, the Democratic minority whip, reportedly is working with Eric Cantor of Virginia, the Republican majority leader, on a resolution that could sharply limit the outlines of a final agreement or call for imposing new sanctions.
Mr. Hoyer’s office described as “preposterous” the notion that he would sign onto any resolution that would undermine the White House. But even a hint that he and other House Democrats might join hard-line Republicans against Mr. Obama on what amounts to a diplomatic breakthrough is alarming.
The outcome of these efforts is unclear. What is clear is that they are not only unproductive but also unnecessary. Congress could, at any point in the future, order tougher sanctions if any deal falls apart.
Equally clear is that such efforts will almost certainly enrage Iran. The interim deal stated that no further sanctions should be imposed while it is in force. New penalties would betray the agreement, feed Iran’s deep mistrust of America, deny Mr. Obama negotiating flexibility, and most likely, crush any hope of a diplomatic solution.