CHICAGO, Aug 19 (Reuters) – Democratic presidential candidate Kamala Harris made a surprise appearance at the party’s national convention on Monday night, 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 Monday, the first night of a four-day event in Chicago.

Harris paid tribute to Biden. “Joe, thank you for your historic leadership, for your lifetime of service to our nation,” Harris said. “We are forever grateful.”

The audience held up placards reading “USA” and “We vote, we win” as Harris entered, and banged together noisemakers.

Biden’s address will cap 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 try to make history as the first woman, a Black and Asian American, to hold the nation’s highest office.

Democrats also cheered their failed 2016 presidential candidate, Hillary Clinton, whose loss to Trump in 2016 dashed hopes of installing the first woman in the White House.

Clinton, who became the first woman to secure a major U.S. party’s presidential nomination, drew a standing ovation as she took the stage on Monday.

“The story of my life and the history of our country is that progress is possible, but not guaranteed,” said Clinton, who also lost her bid for the 2008 nomination to Obama.

She praised Biden for bringing decency, dignity and competency to the White House.

“And now, we are writing a new chapter in America’s story,” Clinton said. “Kamala has the character, experience and vision to lead us forward.”

Clinton took several shots at her former nemesis. “Donald Trump fell asleep at his own trial, and when he woke up, he made his own kind of history, the first person to run for president with 34 felony convictions,” she said to laughter.

Earlier, United Auto Workers President Shawn Fain, mimicking Trump-supporting wrestler Hulk Hogan at the Republican convention last month, tore off his jacket to reveal a T-shirt reading “Trump is a scab. Vote Harris” as the audience cheered.

“The American working class is fired up and fed up,” Fain said as the audience chanted “Trump’s a scab” and held up “Union Yes” signs.

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.

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.

Biden’s wife, Jill Biden, and his daughter, Ashley Biden, were scheduled to speak before him.

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.

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.

Gaza was not mentioned often in the speeches.

Progressive U.S. Representative Alexandria Ocasio-Cortez praised Harris as “working tirelessly to secure a ceasefire in Gaza and bringing hostages home.”

“We have to help her win,” she said.

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.

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.

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.