President Obama’s agreement with the Supreme Leader of Iran threatens our safety and will be remembered as one of the greatest diplomatic failures in American history. If elected president, I would terminate the deal on day one.

Now is no time to hesitate. Congress should vote against this disaster, and all Republicans and Democrats should repudiate it.

But President Obama, Hillary Clinton and other defenders of the deal are pulling out all the stops to keep it in place. Despite the obvious harm the agreement is doing to America and our allies, they are saying we have no choice but to accept it. They paint those who oppose the president’s diplomatic retreat as naive war mongers.

They couldn’t be more wrong. From the beginning, the only thing naive about this entire situation has been the president’s insistence on striking a deal that rewards the world’s leading state sponsor of terrorism for its long history of aggression against America and our allies.

By dismantling sanctions without demanding the Iranians dismantle their nuclear program, President Obama is throwing all of our leverage over the mullahs out the window. And it gets worse. Now we are learning the administration may not have submitted secret side agreements between Iran and the International Atomic Energy Agency (IAEA) to Congress, as required by law.

The Iran deal is just the latest in a series of dangerous foreign policy decisions under the Obama-Clinton doctrine. This is yet another reason why Hillary Clinton must be stopped in 2016. She and other defenders of the deal have betrayed the American people and our closest allies, especially Israel. She has also backtracked on her previous tough talk—such as saying Iran doesn’t have a right to enrichment, which this terrible deal allows.

Clinton is showing us yet again how she and President Obama have left the world less safe and more chaotic than when they took office.

But the deal is more than just dangerous, it is disrespectful to all of the Americans who have suffered at the hands of the Iranian regime.

All of this reminds me of when my brother David and I tied ribbons around the tree in front of our house during the 444 days Iran held 52 Americans hostage. One of them was Kevin Hermening, who grew up in Oak Creek, Wisconsin. He was the youngest hostage, a Marine working at the U.S. Embassy in Tehran.

Kevin was with me the day I announced I was running for president. He has seen the face of the Iranian regime up close. He understands far too clearly what President Obama and Hillary Clinton refuse to recognize: Tehran cannot be trusted, and it has not changed much since Kevin and the other hostages were released on President Reagan’s first day in office.

Kevin and his fellow hostages are not alone. Hundreds of American service members died in Iraq after being targeted by Iran’s Quds Force, a special operations unit that reports directly to Iran’s supreme leader. In his haste to bend to Iran’s will, President Obama seems to have forgotten this fact. Under the terms of his deal, sanctions against the head of the Quds force will be lifted.

Iranian violence against American citizens continues to this day.

Right now four Americans are detained or missing in Iran. Marine veteran Amir Hekmati is one of them. The Iranian authorities arrested him while he was visiting the country to see his grandmother. Convicted in a secret trial of “cooperating with hostile governments,” Hekmati was initially sentenced to death, though the Iranians now seem content to keep him languishing in prison, torturing him and using him as political bait.

Freeing Amir and other Americans like him from the chains of Iranian oppression should have been a priority for President Obama. Despite all of his concessions to Iran, he couldn’t even bring these Americans back home to their families? That’s a national disgrace. It’s as if the president believes Iran is the superpower, and we are the rogue nation on the ropes.

The next president must restore American leadership and strength in the world. We can begin by terminating the Iran deal.

Given how far the administration has gone in accommodating Iran and circumventing the elected representatives of the American people, this won’t be easy. But we need clear and decisive leadership that begins on day one, when the next president must terminate the deal, re-impose existing sanctions, work with Congress to impose new crippling sanctions, and convince our allies to do the same. To signal anything other than immediate rejection of this deal would be to accept the Obama-Clinton argument in support of it.

America, our allies and all of those who suffered harm at the hands of this rogue Iranian regime deserve more than what President Obama and Secretary Clinton have offered. They deserve a new president who will put their safety first and terminate this bad deal with Iran on day one.

Scott Walker, a Republican, is the governor of Wisconsin and a candidate for president.