Former Democratic New York Mayor Ed Koch recently expressed disappointment in President Obama’s treatment of Israel, telling a Jewish crowd last weekend that no one "can rightfully say that President Obama is the best president" for Israel.

"I hope to move the president in further support of Israel," Koch told a largely Jewish audience on Sunday during The David S. Wyman Institute for Holocaust Studies’ national conference in New York City. "I hope to change him."

Koch, a frequent critic of the Obama administration’s policies toward Israel, said Obama could allay the Jewish community’s concerns by simply stating that the United States will no longer tolerate Iranian aggression.

"All of this could be wiped out in terms of bitterness if the president were just to say an attack by Iran on Israel will be perceived by the U.S. as an attack on the U.S., and we will respond militarily," Koch said, according to video of the event.

A respected Democratic voice on the Jewish speaking circuit, Koch’s comments indicate that the White House has failed to woo one its principal Jewish critics as Election Day draws near.

With the Jewish community poised to play a critical role in several key swing states, Koch’s public attacks on the president could become a thorn in Obama’s side.

"He disagrees, to say the least, with President Obama on Israel," Glenn Richter, a longtime Jewish activist who attended Koch’s speech, told the Free Beacon. "He hopes to have some impact on changing his policy."

During the daylong conference, "The Jewish Vote, the Holocaust, and Israel," Koch recalled a 30-minute powwow he had with Obama following the president’s controversial remarks last year pressuring Israel to revert to its 1967 borders.

The White House, Koch recalled, phoned him to arrange a private meeting with the president to discuss the demand that Israel retreat to a set of borders that would leave it more vulnerable to terrorist attacks.

Koch said he told Obama that it was wrong for him to apply pressure on the Israelis, but little on recalcitrant Palestinian leaders.

"I said to him, ‘Mr. President, I would not have been so critical of you when you said that Israel has to go back to the 1967—even though they’re indefensible and I disagree with you—had you also made demands upon Hamas, but you didn’t,’" Koch recalled. "You left them out completely. You didn’t say Israel doesn’t have to deal with them till they give up their charter, violence, etc."

Didn’t I? Obama responded, according to Koch.

"I said, ‘No, Mr. President, you did not,’" Koch said.

Koch drew national headlines in July 2011 when he endorsed New York Republican Bob Turner in the race to replace disgraced former Democratic Rep. Anthony Weiner (D., N.Y.).

The former three-term mayor helped transform the Weiner race into a referendum on Obama’s Israel policies, leading Turner to victory in a congressional district that had not voted Republican in 89 years.

"I want him to know I disagree with his positions as they relate to a number of issues concerning the Jewish community," said Koch, who was seated next to Turner during the event Sunday. "I’m sending a message to the president of my party."

Turner explained that Koch helped galvanize Jewish voters, proving that they are not blindly devoted to the Democratic Party.

"The Jewish vote, which had historically been a bloc, now isn’t, at least on these issues," Turner said.

Jewish voters, who comprise about two percent of the population, have historically embraced the Democratic Party by wide margins—though that support may be eroding.

While Jews overwhelmingly embraced Obama in 2008, with around 78 percent voting in his favor, new polls suggest that the president has lost a significant amount of support.

Pew reported earlier this month that Jews are increasingly less likely to identify with the Democratic Party.

"The size of the Democratic Party advantage has diminished from 52 points in 2008 to 38 points today," Pew reported.

Another poll by the American Jewish Committee showed that in Florida—a heavily Jewish swing state with national implications—Obama is receiving less support than in past years.

Republicans are hoping that a significant number of Jewish voters will abandon Obama following four years of chilly relations with Israel.

Leaders like Rep. Debbie Wasserman Schultz (D., Fla.), who serves as chair of the Democratic National Committee, have struggled to explain Obama’s record, often resorting to lies and subterfuge in interviews.

Wasserman Schultz erroneously claimed that the Israeli ambassador to the U.S. had called Republicans "dangerous for Israel." When confronted about the lie, Wasserman Schultz doubled down, refusing to admit she had fibbed.

The Democratic Party’s recent attempt to drop several pieces of pro-Israel language from its platform also has been viewed as a reason Jews may be souring on Obama.

Tensions between the Jewish community and the Democrats were stoked earlier this month at the party's convention in Charlotte, N.C., when it came to light that the party had omitted references to Jerusalem as Israel’s capital, as well as other pro-Israel planks, from its platform.

The episode was widely condemned by Jewish politicians on both sides of the aisle, and ultimately led to a hotly contested floor vote in which Democratic convention-goers booed the pro-Israel language.

"I was extremely, extremely disappointed at that moment in the Democratic Party," said Richter, the Jewish activist who identified himself as a longtime Democrat.