The three-day poll, which closed on Wednesday, showed 56% of respondents who identified themselves as Democrats said they were less likely to support a candidate who backs military assistance for Israel, compared to 40% who said they would be more likely to support such a candidate.

The poll results illustrate a potentially critical vulnerability for Biden, who has angered some within his party by supporting Israel in its war against Hamas militants, ahead of a close November election in which Biden will be loath to lose any support within his party.

Biden and his likely Republican opponent, former President Donald Trump, were tied with 36% support each in a hypothetical matchup, with the rest of poll respondents saying they were not sure or would vote for someone else or no one at all.

Biden's early and vocal support of Israel and his refusal to condition military aid on a change in military tactics has sparked outrage in his party.

On Tuesday, more than 100,000 Michigan voters in the Democrats' presidential primary cast "uncommitted" ballots in a massive protest to Biden's support for Israel's military campaign.

Democrats' anger has grown as the Gaza death toll climbs, famine looms and much of the territory's 2.3 million population has become homeless.

The war in Gaza started when Hamas militants attacked Israel on Oct. 7, killing 1,200 people and capturing 253 hostages according to Israeli tallies, triggering a devastating military response from Israel that has resulted in 30,000 deaths.

A growing minority of Democrats pin the blame for the conflict on Israel's government, which the United States has long pressured to grant some kind of statehood to a Palestinian territory.

Twenty-two percent of Democrats in the poll blamed the Israeli government for the conflict, compared to 13% in the November poll. Democrats also overwhelmingly said they wanted a presidential candidate who would call for a ceasefire in the conflict.

Some 46% of Democrats in the Reuters/Ipsos poll said they blamed Hamas, down from 54% in a November poll.

While Biden has tried to balance his support for Israel with calls for its military to do more to avoid civilian casualties, Trump has voiced full-throated support for the U.S. ally, a position that appeared in line with the views of many Republicans.

Some 62% of Republicans in the poll said they preferred a presidential candidate that favors supplying Israel with military aid, while 34% said that stance was a turnoff.

Relative to Biden, Trump has staked out a vastly different position on the America's role in the NATO alliance, telling supporters in February that he once told the leader of a NATO ally that he would encourage Russia to attack the country if it were not meeting its financial obligations in the alliance.

In the new Reuters/Ipsos poll, 55% of Republicans said they agreed with a statement that the United States must support democratic countries when they are attacked. Forty percent disagreed.

Among Democrats, 75% agreed and 23% disagreed.

The nationwide poll, which was conducted online, surveyed 1,185 U.S. adults and had a margin of error of about 3 percentage points.