CHICAGO >> President Joe Biden prepared to cement the Democratic Party’s embrace of Vice President Kamala Harris as its leader today in the fight for the White House against Republican Donald Trump.

While Democrats gathered for their national convention, thousands of protesters assembled at a nearby park to pressure delegates to drop the party’s military support for Israel’s Gaza offensive.

The pro-Palestinian protesters were fewer than the tens of thousands that organizers had predicted, but a splinter group left the main march and breached a security perimeter near the convention center, drawing riot police who detained four people.

Biden’s appearance at the start of the four-day event caps a dramatic handover to his No. 2 after he was pressured to quit the race last month by party leaders worried the 81-year-old incumbent was too old to win or serve another four years.

Having served as vice president to the first Black U.S. president, Barack Obama, Biden bowed out of the race to allow his own second-in-command to make history as the first woman, a Black and Asian American, to hold the nation’s highest office.

Harris, 59, was likely to join Biden on stage, sources said. She will formally accept the nomination on Thursday night. Americans go to the polls on Nov. 5.

During a walkthrough of the convention center on Monday afternoon, Biden was asked if it was a bittersweet moment.

“It is a memorable moment,” he told reporters.

Due to speak at 10:50 p.m. Eastern time (0250 GMT on Tuesday), Biden will portray the Republican former president as a threat to American democracy while touting the achievements of the Biden-Harris administration.

A NOTE OF UNCERTAINTY

The pro-Palestinian protests injected a note of uncertainty into what is otherwise likely to be a week of celebration, with some on the party’s left flank angry over the Biden administration’s support for Israel’s actions in Gaza.

Hala Hijazi, a business executive from San Francisco, broke down in tears as she spoke to a panel on the war in Gaza attended by 300 people.

“I’m here because I’ve had over 100 of my family killed in Gaza, two just last week,” Hijazi said. “I’m here in their honor. I’m here because they can no longer speak. After all, that’s the least I can do as an American, as a person of faith and as a Democrat.”

The protesters appeared unlikely to pressure Democrats to change. The party voted on Monday to approve a 92-page policy platform that does not call for an arms embargo against Israel, a demand of pro-Palestinian groups. The United States approved $20 billion in additional arms sales to Israel on Tuesday.

Harris is riding a historic whirlwind into the convention: her campaign has broken records for fundraising, packed arenas with supporters, and turned opinion polls in some battleground states in Democrats’ favor.

Harris’ vice presidential running mate, popular Minnesota Governor Tim Walz, was greeted with chants of “We’re not going back” on Monday when he met with groups of delegates.

One prominent backer, however, cautioned fellow Democrats not to be overly optimistic. “Our numbers are much less rosy than what you’re seeing in public,” said Chauncey McLean, who heads Future Forward, a committee that has raised hundreds of millions of dollars to help elect Harris.

Biden abandoned his reelection bid after his disastrous debate against Trump on June 27 prompted longtime allies, major donors and other party supporters to demand he step aside.

Polls a month ago showed Trump with a clear lead over Biden, but Harris has closed the gap both nationally and in many of the highly competitive states, including Pennsylvania, that will play a decisive role in the election.

“Democrats are fired up,” Wisconsin Governor Tony Evers told reporters. “We have a Republican candidate that is sitting there talking gibberish.”

Harris will call this week for raising the U.S. corporate tax rate from 21% to 28%, her campaign said, which would partially undo one of Trump’s signature accomplishments during his 2017-2021 White House tenure.

TRUMP ON “COMRADE KAMALA”

Trump, meanwhile, plans to campaign this week in battleground states that are likely to determine the outcome of the election.

Some major allies and donors have been urging Trump to steer clear of racial and gender-based insults of Harris and focus his attacks instead on her policy record.

At a small business in southern Pennsylvania, he repeatedly referred to Harris as “Comrade Kamala” in an effort to paint her as a communist at an event to discuss economic policies.

Democrats will also pay tribute on Monday night to their failed 2016 presidential candidate, Hillary Clinton, whose loss to Trump in 2016 dashed Democrats’ hopes of installing the first woman in the White House. She was scheduled to speak before Biden. Other speakers included Biden’s wife, Jill Biden, and his daughter, Ashley Biden.