During an appearance before Jewish voters in Livingston, N.J., last week, Robert Menendez flinched. Mr. Menendez is seeking to win the Senate seat to which he was appointed last year by Governor Corzine.

I was on the panel asking questions of both Mr. Menendez, and once he was finished, his Republican challenger, Tom Kean Jr., now a senator in New Jersey’s Legislature. After a few rounds of questions, audience members began sending up their questions, written on index cards. If it was about foreign affairs, the card was passed to me. So it fell to yours truly to ask Senator Menendez, on behalf of an anonymous audience member, why he was supporting a “nobody” like Ned Lamont over Joe Lieberman in Connecticut’s Senate race.

“I didn’t support Ned Lamont and not Joe Lieberman,” Mr. Menendez said, “so I don’t know where the questioner gets their question. The reality is I am privileged to serve with Joe Lieberman. I think he is a tremendous United States Senator and certainly I supported him when he was running in his primary. So the answer is Joe Lieberman is a great United States Senator and I wish him luck and hope he returns.”

Sounded like an endorsement to me. But ending what the New York Times characterized as “one of the most short-lived endorsements that Senator Joseph I. Lieberman has received in his independent quest for re-election,” Mr. Menendez backtracked. The following day, his spokesman, Matthew Miller, told the Times and other press outlets that “What he was meaning to say is that he has enjoyed working with Senator Lieberman and looks forward to serving with him should he be reelected. But his official endorsement is for Lamont, and he supports the party.”

There is a reason that Mr. Menendez’s flinch deserves wider attention. After all, Mr. Menendez could have answered truthfully, relying for cover (if cover was needed) on the Garden State’s senior senator, Frank Lautenberg, who was sitting in the front row throughout the exchange. Agree or disagree on this or that position, only a fool would argue that Mr. Lautenberg is weak on Israel. Since the primary in which voters defeated Mr. Lieberrman, Mr. Lautenberg has backed Mr. Lamont.

Mr. Menendez flinched because he knows that supporters of Israel are rightly anxious that the party engaged in excessive Bush-bashing could throw the president’s Israel policy out with the Iraqi bathwater. Nor is this anxiety merely the product of a GOP campaign to paint the Dems as “loony leftists” who will sell Israel down the river.

I have no doubt that Mr. Menendez is pro-Israel, along with many other liberals now standing for reelection, like Tom Lantos and Howard Berman of California. But there are worrisome trends.

Take, for example, the new book by President Carter, “Palestine: Peace not Apartheid,” whose title signifies that Israel is practicing a policy akin to the hateful racism of the former South African regime. Regarding the Lebanon conflict, a Pew poll released on August 17 found “most Republicans (53%) believe Israel’s actions have been about right, while just 11% believe they have gone too far. Democrats are divided on this question, with only about a third (35%) saying Israel’s actions have been appropriate and another third (31%) saying they have gone too far.”

Or take the new survey released just a few days ago by the Program on International Policy Attitudes, an organization located in Washington, D.C., that researches public opinion on international issues, titled “What Kind of Foreign Policy Does the American Public Want?” According to the PIPA findings, “Americans see U.S. policies as contributing to negative attitudes toward the United States in the Middle East. Asked what contributes to these negative attitudes, 62% attribute them to ‘dislike of American policies’ in the region, compared to 34% who say ‘dislike of American values.’ Democrats are far more likely to cite policies (78%) than values (20%), while Republicans tend to choose values (59%) more than policies (38%).” Those attributing America’s difficulties in the Muslim world to “values” believe that the two have conflicting ideas about freedom as well as conflicting interests. Those attributing the low regard in which America is held in Muslim countries to “policies” believe that America is being punished for supporting Israel (as well as autocratic regimes).

Even Mr. Menendez felt the need to play to these Democrats by criticizing Mr. Bush regarding Israel, arguing that his presidency lacked the “constant engagement” in pursuit of Middle East peace, which was a key feature of the Clinton presidency. This has become a commonplace Democratic critique of the Bush presidency. Distracted and weakened by Iraq, Mr. Bush is alleged to have “missed opportunities” for Israel-Palestinian peace.

But the real problem has been the Palestinians’ inability to deliver. Mr. Bush came into office as the second intifada broke out and as Prime Minister Barak was about to lose an election to Ariel Sharon, then seen as an inveterate hard-liner. Mr. Clinton came into office just after Labor returned to power in Israel behind Yitzhak Rabin and then presided over the Oslo breakthrough and the Rabin-Arafat handshake on the White House lawn eight months into his first term. Mr. Clinton’s policies were appropriate for that time frame and those circumstances. Mr. Bush’s have (by and large) been appropriate for this time frame and these different circumstances.

So this flinch is really part of a bigger picture in which some voters worry not about Robert Menendez per se, but about the wing of the party that will sweep into power along with the pro-Israel liberals, a problem about which pro-Israel liberals prefer to be in denial. The Menendez Flinch was the consequence of the cognitive dissonance between the pro-Israel liberalism practiced by Mr. Menendez, et al., and the strong undercurrents within the Democratic voting base pulling in other directions.

Mr. Twersky is a contributing editor of The New York Sun.