Months after a sudden surge of anti-Semitic hate crimes in New York City, Jewish community leaders are still struggling to identify a clear cause for the jump.

Anti-Semitic crimes more than doubled from 36 to 80 incidents between the third and fourth quarters of 2018, and the number of incidents remained high through the first six months of 2019.

The motivations for the attacks remain murky, but Jewish community leaders do not accept Mayor Bill de Blasio's offered explanation — that right-wing ideology is the root cause. De Blasio addressed the growing number of incidents in June, pointing his finger at conservatives and arguing that “the ideological movement that is anti-Semitic is the right-wing movement."

In fact, the victims of the attack tend to lean Right, rather than Left. David Pollock, associate executive director at the Jewish Community Relations Council of New York, told the Washington Examiner that anti-Semitic attacks, in addition to becoming more violent, particularly target “those that are physically identifiable as Jews: Orthodox males."

Orthodox Jews are more conservative than their conservative and reform brethren, and President Trump performed well among Orthodox Jews in 2016, at least in part due to his staunch support of Israel.

Deborah Lauter, who directs de Blasio’s hate crime office, which launched earlier this week, said Tuesday there are other motivations behind the anti-Semitic crimes.

“He’s correct to say there are threats that come from the right wing. There are also threats that come from the Left,” said Lauter, who later added she was “not aware” of a right-wing threat of anti-Semitism in New York.

Anti-Semitic hate crimes held steady during the first nine months of 2018, ranging from 31 to 41 incidents per quarter, prior to jumping during the final quarter. Between October 2018 and June 2019, the number of incidents ranged from 66 to 80 per quarter.

Pollock categorized some of the perpetrators but said uncovering a reason behind the increase in attacks is challenging.

“There’s a category of teenagers getting into bad things. There’s a category of mentally ill individuals … people who evidently have psychiatric issues” as well as “deep-seated anti-Semitism,” said Pollock.

He also observed that many perpetrators are minorities, and so “white nationalism seems to be out” as an explanation.

Police department statistics regarding hate crime perpetrators in 2018 show 55% of suspects were black, almost 24% were white, and 20% were Hispanic. Out of over 350 suspects, however, police only knew the race or ethnicity of 39.1%.

Pollock also dismissed the idea President Trump was contributing to the attacks.

"I don’t think we can blame the president for this. There’s no clear nexus on that. Are these guys on Trump’s Twitter feed? I doubt it," said Pollock.

Pollock highlighted the difficulty in identifying motives by pointing to a spate of anti-Semitic attacks in Brooklyn’s Crown Heights neighborhood, which has a large Orthodox Jewish population, during the first half of 2019.

“In general, the police found the perpetrators, arrested the perpetrators, and the perpetrators would not talk,” said Pollock.

In one incident in Crown Heights last month, a man threw a brick at an Orthodox Jewish rabbi while he was exercising, leaving the rabbi with face, head, and leg injuries.

Other attacks on New York City’s Jewish community are not reported as hate crimes. On Sunday, for example, a Jewish father and son were stabbed after getting into an argument with three men drinking outside a synagogue in Brooklyn’s Borough Park neighborhood.

Michael Schmidt, director of American Jewish Committee-New York, echoed Pollock’s remarks, saying there is no apparent “common thread” to the attacks.

“When we look at the different incidents and we try to see whether there is a common pattern in them, so far we have not been able to identify a common pattern,” Schmidt told the Washington Examiner.

Although an explanation for the crimes remains elusive, there are some other factors potentially contributing to an increase in attacks. Schmidt cited New York’s large Jewish population and a “heightened awareness within the Jewish community to report incidents.”

“I think we’ve learned and seen from our Jewish community in Europe and elsewhere that we can’t remain quiet, we can’t be victimized, and we need to feel empowered and speak out,” said Schmidt.