At the annual J Street conference in Washington, Democratic presidential hopefuls were questioned on whether they would condition U.S. aid to Israel on the Jewish state not annexing any part of the West Bank.

In a presidential forum hosted by former Obama administration officials Ben Rhodes and Tommy Vietor, candidates were pressed to express their willingness to take a tougher stance on the U.S.-Israel relationship.

Vermont Senator Bernie Sanders (I-VT) took the hardest line of any of the attending candidates, telling Rhodes and Vietor that Israel will have to “fundamentally change” its relationship with Gaza if it wants continued military aid. Sanders has long been supportive of conditioning U.S. aid to Israel and using it as leverage to change the behavior of Prime Minister Benjamin Netanyahu’s government, which he has repeatedly described as “racist.”

South Bend Mayor Pete Buttigieg told attendees that he would support conditioning U.S aid as a means to discourage Israel from attempting to annex parts of the West Bank. The Democratic hopeful, who visited Israel last year, said the United States needs to “have mechanisms to do this to make sure U.S. taxpayer support for Israel doesn’t turn into U.S. taxpayer support for a move like annexation.” He also argued that “U.S. policy should not be promoting settlement construction because it is incompatible or at best detrimental to what we need to see happen” in the region. Buttigieg added, “you can be committed to the U.S.-Israel alliance without that entailing support for any individual choice of a right-wing government over there.”

Former Secretary of Housing and Urban Development Julian Castro struck a more cautious note. Castro, who served in the cabinet from 2014-2017, would not take the idea of conditioning aid “off the table” but argued that the United States already has a “carrot-and-stick approach.” Castro expressed the hope that “we’re going to have a new [Israeli] government to work with our ally to ensure that there is not unilateral annexation and that we pursue a two-state solution.”

Colorado Senator Michael Bennet echoed Castro’s caution. “I would not rule out” conditioning American aid to Israel, said the two-term senator. However, he was hesitant to embrace it, worried that “if we pick one instrument like that in this town, it very quickly is going to become a partisan litmus test.” The Colorado Democrat also made clear that while he didn’t believe Israel should be building settlements and that the United States should be doing “everything we can to limit settlements,” Bennet also warned that the current Israeli government “basically has a permission slip from [the] Trump administration to do whatever they want.”

Speaking on Sunday, Minnesota Senator Amy Klobuchar (D-MN) dodged the question. “It is not a good idea to negotiate these things right now,” said the Minnesota Democrat. She disagreed with Netanyahu’s September announcement that he would begin to annex settlements on the West Bank if re-elected, calling it “wrong.”

Other candidates submitted videos instead of attending the forum. In her video, Senator Elizabeth Warren (D-MA) said, “If Israel’s government continues with steps to formally annex the West Bank, the U.S. should make clear that none of our aid should be used to support annexation.” In contrast, former Vice President Joe Biden said in a video that Israel should stop “settlement activity which takes us further from peace” and warned about support for the Jewish state becoming “a political football.”

Former Congressman Beto O’Rourke, businessman Andrew Yang and author Marianne Williamson also submitted videos to the liberal group, which advocates a dovish Middle East policy.