2020 Democratic candidates were surprisingly critical of the Iran nuclear deal during the first presidential debate.

Signed by the Obama administration in 2015, the accord between Iran, the US, European powers, Russia, and China put tight restrictions on Tehran’s nuclear program in exchange for sanctions relief. The Obama administration’s goal was to block Iran’s path to a nuclear weapon diplomatically instead of by force.

Critics have long said the deal was imperfect because it didn’t cover other aspects of Iran’s behavior, including its support for terrorism and its growing missile program that can threaten US allies in the Middle East and Europe.

Iran had no interest in putting those elements, which are key parts of its foreign policy, on the table in negotiations. But in order to cap Iran’s nuclear ambitions, the Obama administration decided to sign a targeted, limit accord. (Iran has never officially said it seeks a nuclear weapon.)

Democrats vying to be the next president, though, took aim at the deal, which President Donald Trump withdrew from last year because he wanted to place even more pressure on Iran to change its ways. Many believe that decision has led to the two-month standoff between the US and Iran and potentially put both countries on the path to war.

NBC’s Lester Holt asked the candidates to raise their hands if, as president, they would rejoin the 2015 nuclear deal as originally negotiated. Every candidate on the stage raised their hand — except Sen. Cory Booker (D-NJ).

“We need to get into a deal, but I’m not going to have a platform to say I’m going to rejoin the deal,” he explained. “When I’m president of the United States, I will do the best I can to secure the country and the region, and if I have an opportunity to leverage a better deal, I’m going to do it.”

In other words, he didn’t want to put himself in a corner. If the opportunity arose to somehow get the Iranians to put their support for terrorism on the table, for example, Booker would want to talk to them about that.

But he wasn’t alone in seeking to add on to the Iran nuclear deal. “It was imperfect, but it was a good deal for that moment. I would have worked to get longer sunset periods, and that’s something we can negotiate to get back in the deal,” Sen. Amy Klobuchar (D-MN) said, referring to the limited amount of time some of the restrictions on Iran’s nuclear program last under the current deal.

Rep. Tulsi Gabbard (D-HI) piled on: “We need to get back into the Iran nuclear agreement and we need to negotiate how we can improve it,” she said. That was surprising, since she has made a name for herself with her strong antiwar and nonaggressive foreign policy views.

More surprising, though, was just how critical the Democratic candidates were of the Obama-era nuclear deal.

Why 2020 Democrats took the Iran deal to task

Having three Democratic candidates criticize the strength of Obama’s deal, which has long been held as an accomplishment by left-wing politicians, was unexpected and surprising. But there may be two reasons why that happened.

First, it’s hard for candidates not to be tough on Iran right now, especially since it recently shot down an expensive US military drone and has long threatened American troops in the Middle East.

Second, the frontrunner in the race is Joe Biden, Obama’s vice president. Criticizing the Obama administration’s signature foreign policy accomplishment is surely a sideswipe at Biden, and it could put him on the defensive over the next few weeks.

It’s unclear if left-wing presidential hopefuls will continue to talk tough about Iran and push for a more comprehensive accord. But what is clear is that the Iran deal’s relative unpopularity was one of the surprises of the first debate.