Benjamin Netanyahu, Israel's prime minister, waves while arriving to speak during the American Israel Public Affairs Committee (AIPAC) policy conference at the Washington Convention Center in Washington, D.C., U.S., on Monday, March 2, 2015. Netanyahu's plans to lash out at the emerging U.S.-led nuclear deal with Iran in Congress this week will generate nearly as much anger among his opponents at home as at the White House. Photographer: Andrew Harrer/Bloomberg *** Local Caption *** Benjamin Netanyahu Benjamin Netanyahu, Israel’s prime minister, waves while arriving to speak during the American Israel Public Affairs Committee policy conference in March. (Andrew Harrer/Bloomberg)

The Iran deal is as big a threat to Israel as any event since the 1973 Yom Kippur War. The American people as a whole by a large majority oppose it, and yet a Democrat from New Jersey, Sen. Cory Booker, who has had excellent relations with the pro-Israel community, cannot bring himself to oppose the deal even after it is certain there are enough votes to sustain a veto. Moreover, his statement acknowledges just how flawed the deal is.

One can attribute Booker’s vote to a singular act of political cowardice, but upon closer inspection it is one more dispiriting sign of a trend we have seen for many years: There is no longer true bipartisan support for Israel. There is one party, the Republican Party, for whom support for Israel is a litmus test (largely due to evangelical support for Israel) and a few stray elected officials on the other side. Sens. Chuck Schumer (D-N.Y.) and Robert Menendez (D-N.J.) are the rare exceptions.

Now, one cannot say the pro-Israel Jewish community did not try to win over Democrats. It went all out with ads, lobbying and private pleas. It did not win the day because for Democrats it is simply too risky to take a pro-Israel vote defying the left, which has become at best indifferent to Israel and at worst antagonistic. With only downsides, someone like Booker crumbles in the face of White House pressure.

That suggests some real soul-searching is needed for groups such as the American Israel Public Affairs Committee, which always claimed to deliver bipartisan support for Israel. It cannot. It did not, when it mattered most. No issue was more important to AIPAC and Israel than the Iran deal, and they could not win over someone like Booker.

Simply cheering those who stand by Israel is not enough any longer because, in effect, the vast majority of elected Democrats won’t come to Israel’s aid when the vote is hard. That suggests a rethinking of its approach and a more overtly political mission. If it supports for office only those who really do support Israel when the chips are down and oppose (by primary if need be) incumbents whose votes are contrary to the cause of a strong U.S.-Israel relationship, it might avoid debacles in the future. To hold a convention next year embracing the Democratic presidential nominee and/or Democratic lawmakers who supported the deal turns the group into a cover for anti-Israel votes. It betrays its own mission.

Perhaps AIPAC and other Democratic-leaning pro-Israel groups need to address the glaring lack of support for Israel on the left by outreach and education. But then to be effective they will need to put muscle and money behind efforts to support only truly pro-Israel candidates. That means supporting a primary challenge to Booker when he is up for reelection and, if Booker survives, his opponent. How else could the group have any credibility?

However pro-Israel groups address the issue, the sad fact remains that they can no longer support liberal Democrats expecting them to support Israel on crucial matters. The most anti-Israel president in history, President Obama, and the flock of Democratic lawmakers who supported him despite the wishes of their constituents should tell them something. Democrats (a majority of AIPAC members) need to consider if their support for the Democratic Party is inconsistent with their support for Israel. The Iran vote suggests it is.