Attendees walk past a sign at the United Center, ahead of the Democratic National Convention (DNC) in Chicago, Illinois, U.S., August 19, 2024. / REUTERS/Mike Blake

CHICAGO (Reuters) -Democratic presidential candidate Kamala Harris made a surprise appearance at the party's national convention on Aug.19, drawing cheers from the crowd as she vowed to defeat Republican rival Donald Trump in the November election.

"Let us fight for the ideals we hold dear and let us always remember, when we fight we win!" Harris, the U.S. vice president, said in brief remarks that drew roars from the crowd.

She had been expected to appear later with President Joe Biden, the keynote speaker, on the first night of a four-day event in Chicago.

At the start of the four-day event, Biden's appearance 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 second-in-command to try to make history as the first woman, a Black and Asian American, to hold the nation's highest office.

Hillary Clinton, who became the first woman to secure a major U.S. party's presidential nomination, was due to address the gathering later on Aug.19.

Clinton fell short two times, losing the party's nomination to Obama in 2008 and the election to Trump in 2016 in a bitter disappointment for the pioneering but polarizing political figure.

During a walkthrough of the convention center on Aug.19 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 Aug.20), 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

While Democrats gathered for their national convention, thousands of people assembled at a nearby park to protest 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.

The 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, because 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 Aug.19 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 recently.

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" 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 to raise the U.S. corporate tax rate from 21 percent to 28 percent, 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" to paint her as a communist at an event to discuss economic policies.