Democrat presidential candidate Bernie Sanders said on Sunday he would skip The American Israel Public Affairs Committee's (AIPAC) annual policy conference, citing his concern that the pro-Israel lobby group provides a platform for leaders expressing "bigotry" and opposition to "basic Palestinian rights".

Making the announcement via Twitter, Sanders pledged that as president he would support the rights of both Palestinians and Israelis, while doing "everything possible to bring peace and security to the region".

The Israeli people have the right to live in peace and security. So do the Palestinian people. I remain concerned about the platform AIPAC provides for leaders who express bigotry and oppose basic Palestinian rights. For that reason I will not attend their conference. 1/2 — Bernie Sanders (@BernieSanders) February 23, 2020

The AIPAC conference, which will take place from March 1 to March 4, is an annual gathering of pro-Israel leaders and personalities in Washington, DC, to highlight ways to strengthen US-Israeli ties and show support for the state of Israel. Sanders' comments led AIPAC to publish a strong rebuke to the senator's refusal.

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"It's pretty major when the Democratic frontrunner announces he's skipping AIPAC," Peter Feld, a progressive campaign strategist and pollster at the digital media company, The Insurrection, told Al Jazeera.

"AIPAC made it impossible for Sanders to go, by running ads against him, but it's significant that he cited anti-Palestinian bigotry as the reason to skip AIPAC," he added.

Feld said that most importantly, for Sanders to make such comments at such a critical moment for his campaign, it shows that Sanders doesn't believe a "fight with AIPAC will hurt him politically, or maybe even helps".

Sanders' comments come only days after his win in the Nevada Caucus on Saturday, solidifying his frontrunner status in the Democratic primary.

In the past, speakers have included Israeli Prime Minister Benjamin Netanyahu, former Secretary of State Hillary Clinton and former US President Barack Obama. All three have attended the conference multiple times.

Earlier this month, US Senator Elizabeth Warren, another Democrat presidential hopeful, indicated that she too was unlikely to attend the annual conference.

'Truly shameful'

Shortly after his two-part tweet, AIPAC put up a statement calling Sanders's comments "truly shameful".

"Senator Sanders has never attended our conference and that is evident from his outrageous comment," the statement said.

Senator Sanders has never attended our conference and that is evident from his outrageous comment.



Full statement: https://t.co/XDcNKhYXSq pic.twitter.com/aJGJiv2wv8 — AIPAC (@AIPAC) February 24, 2020

AIPAC said a diverse group of people - "Democrats, Republicans, Jews, Christians, African Americans ... participate in the conference to proclaim their support for the US-Israel relationship."

The statement said by his comments, Sanders was "insulting his own colleagues and the millions of Americans who stand with Israel".

Speakers included in this year's conference include Senate majority leader Mitch McConnell, Democratic Senator Bob Menendez, Democratic Congressman Hakeem Jefferies, and House Republican leader Kevin McCarthy.

Established in 1951, AIPAC is the most influential pro-Israel group in the US, raising annually over $100m a year from donors.

'Hate group'

Sanders' rejection and rebuke of AIPAC came on the heels of the organisation's spat with Democratic Congresswoman Betty McCollum. The group sponsored Facebook ads implying that she, along, with US representatives Rashida Tlaib and Ilhan Omar, the first two Muslim women in the US Congress, were anti-Semites.

McCollum responded by calling AIPAC a "hate group" and said it was "weaponizing anti-Semitism and hate to silence dissent" while simultaneously "taunting Democrats and mocking our core values".

The lobby swiftly retracted the ads and issued an apology to Democrats, but not to McCollum herself.

"We offer our unequivocal apology to the overwhelming majority of Democrats in Congress who are rightfully offended by the inaccurate assertion that the poorly worded, inflammatory advertisement implied," the statement read.

Omar Baddar of the Arab American Institute, based in Washington, DC, told Al Jazeera that Sanders' tweets reflected "the shift in public opinion among young and progressive voters who are beginning to see through AIPAC's hypocrisy".

"For far too long, AIPAC has gotten away with a fundamental contradiction: they preached bipartisanship while consistently supporting the most aggressive, anti-Palestinian right-wing policies," Baddar added.

"Now that the Democratic Party base has become much more aware of Israel's violations of Palestinian rights, and much more hesitant to afford a carte blanche for Israel to behave as it wants and evade accountability, the inevitable clash between AIPAC and real progressives who value justice and human rights is finally under way, and is likely to escalate moving forward," Baddar noted.

Some of AIPAC's policy positions include supporting $3.8bn a year in US military aid to Israel, opposing the Boycott Divestment and Sanctions Movement, and supporting moving the US embassy in Tel Aviv to Jerusalem - a step widely opposed by the international community.

AIPAC has also come out in full support of Trump's Middle East plan - unveiled last month - calling it a "solid basis for negotiations".

The plan, an attempt to bring lasting peace between the Israelis and the Palestinians, has been unequivocally rejected by the latter, with Fatah and Palestinian Authority leader Mahmoud Abbas calling it the "the slap of the century".