The flap over Benjamin Netanyahu’s planned visit to Washington, only two weeks before Israel’s general elections, was just what critics of the prime minister needed: a chance to attack his foreign policy credentials and to try and drive home the message that Netanyahu has botched relations with America.

There was little surprise to hear Netanyahu’s rivals from the left, led by Tzipi Livni, Yitzhak Herzog and Yair Lapid, slam the prime minister’s handling of this latest crisis. But less expected was the emergence of a new Netanyahu critic, one that until not long ago was the prime minister’s close confidant and emissary to Washington.

Michael Oren, formerly Netanyahu’s hand-picked ambassador to Washington, who is now running for the Knesset as part of the Kulanu party led by centrist Moshe Kahlon, was the latest to lash out at the prime minister’s conduct.

“The behavior over the last few days created the impression of a cynical political move, and it could hurt our attempts to act against Iran,” Oren told the Israeli website Ynet. “It’s advisable to cancel the speech to Congress so as not to cause a rift with the American government. Much responsibility and reasoned political behavior are needed to guard interests in the White House.”

Oren’s advice on relations with America carries a lot of weight both in Israel and overseas. As the most recent ambassador to Washington who has worked closely with Netanyahu and with the Obama administration, and as a scholar who has researched Israeli-American relations, Oren is perceived as a leading expert....