In his State of the Union address, the President’s core message was that the US has emerged strong from the twin crises caused by the 2001 terrorist attacks and the 2008 global recession.

And the challenge he posed to Congress on foreign policy is this. Do we want to continue to operate in crisis mode – being fearful, reactive, and prone to overuse military force in ways that exacerbate security problems and contradict basic values? Or can Congress support the President’s efforts to exercise “smart” global leadership and to work closely with other countries to address shared threats and protect the planet?

This choice is particularly stark when deciding what to do about Iran’s nuclear program.

Two years of steady progress

Over the past two years, vigorous multilateral diplomacy has accomplished what could not be done so long as memories of the 1979 hostage crisis made diplomatic isolation, military threats and economic sanctions the only policy options that American leaders thought they could use.

While negotiations with the United States and other world powers are moving forward, Iran has suspended or even reversed its most worrisome nuclear activities, and been more transparent about other aspects of its program.

The President underscored some potential benefits of successful diplomacy. Preventing Iran from acquiring nuclear arms makes the US and its allies more secure. Achieving this through multilateral diplomacy means avoiding war with another Islamic country.

Reaching agreement in principle before world leaders gather in New York later this spring to review the Nuclear Nonproliferation Treaty (NPT) is the most important thing that can be done at this point to prevent other countries from making or using nuclear weapons, too.

Obama warned Congress that passing legislation for new sanctions against Iran would not strengthen his hand. On the contrary, it would guarantee the failure of negotiations and go against what the American people want them to do.

“Let me be clear. If this Congress sends me a new sanctions bill now that threatens to derail these talks, I will veto it.”

Public opinion backs the president - Republicans too

Public opinion research conducted by myself and colleagues at the Center for International and Security Studies at the University of Maryland (CISSM) substantiates both of these points.

A decision-making simulation done with the Program on Public Consultation showed that a clear majority of American respondents, including six out of ten Republicans, preferred continued efforts to negotiate a compromise deal that limits Iran’s enrichment, increases transparency, and provides some sanctions relief to the alternative option of ending negotiations and trying to get other countries to impose more sanctions on Iran.

In July 2014 we conducted a joint opinion poll with the University of Tehran Center for Public Opinion Research, where CISSM associate Ebrahim Mohseni is a senior analyst.

This survey also found broad public support among Iranians for potential elements of a deal that are consistent with the principles of the Non Proliferation Treaty (NPT).

At the same time, the poll revealed why previous sanctions never persuaded Iran’s leaders to stop enriching uranium, and why threatening additional sanctions is unlikely to get more Iranian concessions.

A near-unanimous majority (94%) of Iranians say that it is essential for Iran to make peaceful use of nuclear energy. Large majorities would oppose dismantling half of Iran’s centrifuge capability (70%) or accepting limits on nuclear research (75%). We found no significant difference depending on political preferences. In fact, those respondents who were more highly educated were more negative towards measures that would treat Iran differently from other NPT members that have promised not to develop nuclear weapons.

Threatening to impose new sanctions now, or in a few months if Iran has not acquiesced to these maximalist demands, weakens the United States’ negotiating leverage by stoking Iranian doubts that the President could deliver promised sanctions relief.

Before Republicans won control of the Senate, three-quarters of Iranian respondents already expected that the United States would not lift nuclear-related sanctions even if Iran accepted all US nuclear demands.

Significantly, the small percentage of Iranians who expressed confidence that the United States would reciprocate Iranian cooperation was more willing to accept additional limits and transparency measures. This suggests that providing credible reassurance about sanctions relief could help persuade a majority of Iranians to accept limits on centrifuge numbers and enriched uranium stockpiles for the duration of a comprehensive agreement.

The United States’ closest allies in negotiations with Iran have asked Congress not to pass new sanctions legislation. An increasing number of Democrats in Congress now say that it is better to wait and see what type of agreement can be reached with Iran in the next few months.

Some former Republican national security officials, like Brent Scowcroft, have urged Congress to give diplomacy a chance, but it seems that House Speaker John Boehner is not listening.

In a move that directly challenges the President, he has invited Israel’s prime minister to address Congress specifically on the dangers posed by Iran’s nuclear program.

It is worth noting that Benjamin Netanyahu has been more hawkish than his own intelligence agency Mossad, which warned a bipartisan Congressional delegation visiting Israel last week against new sanctions legislation.

The choice for Republican leaders now is whether or not they really want to sabotage the negotiations, against the wishes of the American public and key allies. Doing so would reinforce Iranian suspicions that they are – once again – exploiting international concerns about alleged efforts to build weapons of mass destruction as an excuse for military intervention and regime change.