Speaking to Jewish Republicans on Saturday, Donald Trump claimed a Democratic victory in 2020 could be damaging for Israel. In response, the executive director of a group representing Jewish Democrats lamented the president's “assault on decency and truth” and criticised his remarks about the impending Israeli election.

Speaking at the annual meeting of the Republican Jewish Coalition (RJC), Trump touted two precedent-shredding actions: moving the US embassy to Jerusalem from Tel Aviv and the recognition of Israeli sovereignty over the Golan Heights.

“We got you something that you wanted,” Trump said, adding: “Unlike other presidents, I keep my promises.”

The RJC backed Trump in 2016. It is backed by Sheldon Adelson, a casino magnate and rightwing megadonor. On Saturday, Trump met Adelson before speaking. Adelson and his wife received a standing ovation when they entered the ballroom.

In 2016, the Adelsons gave Trump $30m. They followed that with $100m for Republicans in 2018. In November, Miriam Adelson joined Elvis, Babe Ruth and other famous Americans in being awarded the Presidential Medal of Freedom.

“I know that the Republican Jewish Coalition will help lead our party to another historic victory,” Trump said. “We need more Republicans. Let’s go, so we can win everything.”

Jewish voters are often liberal but Republicans hope to narrow the gap. Trump earned standing ovations for the embassy move and the Golan Heights recognition.

The speech came weeks after he suggested Democrats “hate” Jews, following an internal fight among Democrats over comments about Israel by Ilhan Omar of Minnesota, one of the first Muslim women elected to Congress, that some claimed were antisemitic.

Trump mockingly thanked Omar on Saturday before adding, to laughter: “Oh, I forgot. She doesn’t like Israel, I forgot, I’m sorry. No, she doesn’t like Israel, does she? Please, I apologize.”

It emerged this week that a New York man who said he “loved” Trump has been charged with threatening to kill Omar.

Trump also accused Democrats of allowing antisemitism to “take root” in their party. In a statement released separately on Saturday, the White House claimed the entire slate of Democratic presidential candidates had failed to adequately condemn antisemitism and rejected the need to protect Israel.

The statement came after the former Texas congressman Beto O’Rourke compared rhetoric used by Trump to describe immigrants to rhetoric used in Nazi Germany. O’Rourke spoke in Iowa on Thursday. The White House did not comment then. Instead of directly addressing O’Rourke’s comments, the Saturday statement sought to attack Democrats on the day Trump spoke in Las Vegas.

In a statement, Jewish Democratic Council of America (JDCA) executive director Halie Soifer said: “We strongly denounce President Trump’s continued assault on decency and truth, as was evident in his speech earlier today before the Republican Jewish Coalition in Las Vegas.”

Trump also took credit for eliminating hundreds of millions of dollars in aid to Palestinians and for pulling out of several United Nations organizations, alleging anti-Israel bias in their agendas.

He criticized some Democrats who have suggested they would re-enter the 2015 Iran nuclear deal, from which Trump withdrew. The agreement was fiercely opposed by Israeli prime minister Benjamin Netanyahu, with whom Trump is closely aligned.

Netanyahu is seeking to return to power in Tuesday’s election. Trump predicted that election is “gonna be close”, adding that it features “two good people”, seemingly a reference to Netanyahu and the chief threat to his coalition, former army chief of staff Benny Gantz.

Soifer said: “The US-Israel relationship has been – and must remain – bipartisan, and we unequivocally reject Trump’s ongoing effort to politicize issues related to Israel on the eve of the Israeli election.

“It’s no coincidence that Trump’s Shabbat morning speech in Las Vegas coincides with primetime, post-Sabbath television in Israel, just three days before the Israeli election. Israelis have every right to go to the polls without the US president putting his thumb on the scale in support of any one candidate.”

On Saturday, Netanyahu told Israeli TV he would annex Israeli settlements in the occupied West Bank if he wins, a last-minute promise likely to enrage Palestinians and the Arab world.

Trump has faced his own criticism from the US Jewish community. He was slow to condemn white supremacists who marched violently in Charlottesville, Virginia, in 2017. The previous year, he circulated an image of a six-pointed star alongside a photo of Hillary Clinton, a pile of money and the words “most corrupt candidate ever”.

When he addressed the RJC in 2015 he said he did not expect to earn their support because he wouldn’t take their money.

“You want to control your politicians, that’s fine,” Trump said at the time. Ultimately, the group and many of its donors backed him.

On Saturday, Soifer said: “Trump’s policies and rhetoric are antithetical to Jewish values and … antisemitism has increased to unprecedented levels due to Trump’s divisive words, policies and wilful blindness.

“What happened today in Las Vegas was a shameful display of lies and arrogance.”