(AP) -- Hillary Rodham Clinton turned to her husband, former President Bill Clinton, and pop singer Katy Perry to energize her campaign's faithful Saturday before a pivotal dinner with thousands of Iowa Democrats.

Her chief Democratic presidential rival, Vermont Sen. Bernie Sanders, rallied thousands of cheering supporters before marching across a bridge spanning the Des Moines River, telling them: "This country belongs to all of us, not just wealthy campaign donors."

One hundred days remain before Iowa's leadoff presidential caucuses, and the afternoon events were designed to generate enthusiasm before the state Democratic party's annual Jefferson-Jackson fundraising dinner.

"She's my firework," Perry told Clinton's supporters, wearing a white strapless gown adorned with a Clinton campaign logo and a flowing American flag cape at a free concert.

Bill Clinton told the rally that during the last few weeks the nation has "learned a lot about Hillary, what she's for, why she's running and what kind of president she would be." With tongue in cheek, he complained that he was tired of women having a "stranglehold" on the position of first spouse and hoped to break that White House gender barrier.

More than 6,000 activists were expected at the dinner, which traditionally serves as a kickoff to the Feb. 1 Iowa caucuses.

Clinton and Sanders sit atop a Democratic presidential field that has effectively pared down to a two-person race for the nomination after Vice President Joe Biden announced this week he would not seek the White House.

Former Maryland Gov. Martin O'Malley hoped for a breakout performance at the dinner, which catapulted President Barack Obama in the fall of 2007 and led to his surprising victory in the caucuses.

In the hours before the fundraiser, Iowa's capitol city was full of pageantry as supporters of the three campaigns poured into Des Moines wearing T-shirts and waving signs. Some Clinton enthusiasts painted their cars to show support for the former secretary of state, and her team dispatched young loyalists along street corners to wave signs at passing cars.

Bill Clinton headlined his first campaign rally at the pre-dinner concert featuring Perry, a Clinton backer whose hit song, "Roar," is an anthem at Hillary Clinton events. The former president has raised money for his wife's campaign, but the rally was his first big splash during the race.

Perry got into the act much earlier, recording a wake-up phone message for Clinton's organizers. "Wake-y Wake-y eggs and bakey. It's Katy Perry here," the pop singer said in the call. "I know it's early, but you know what they say, the early bird gets the votes." At the free concert, she performed her hits "Roar," and "Firework," along with a rendition of "America the Beautiful."

The dinner caps a key stretch for Hillary Clinton, who received a boost from Biden's decision not to run on Wednesday and then put together a grinding, competent appearance on Thursday before a Republican-led congressional committee probing the deadly 2012 attacks on diplomatic outposts in Benghazi, Libya.

Two lesser-known rivals, Jim Webb and Lincoln Chafee, abandoned the race following Clinton's strong performance on Oct. 13 in the first primary debate.

The dinner, called the "J-J," is an important showcase for Sanders, a Vermont independent who has drawn large crowds with his calls for a "political revolution" to address the gap between the wealthy and the poor.

Clinton placed third in Iowa in 2008 and has since vowed to build a formidable organization to power her to victory here. She has sought to present herself as the heir to Obama's legacy, while Sanders offers an anti-establishment message and often notes the large numbers of Democrats who stayed home in the 2014 midterm elections.

O'Malley, who has trailed Clinton and Sanders in polls by wide margins, is a member of a Celtic Irish band and broke out his guitar to perform a cover of Johnny Cash's song, "I've Been Everywhere" at a pre-dinner event on Saturday. The ex-governor has campaigned extensively in Iowa and knows the process firsthand: He got his start here as a young field organizer for Sen. Gary Hart's presidential campaign in 1984.

A recent Iowa poll by Bloomberg Politics and The Des Moines Register found Clinton with a slight lead in the state over Sanders, with the two candidates the choice of 9 in 10 voters. O'Malley was at 2 percent.

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On Twitter, follow Ken Thomas at https://twitter.com/KThomasDC and Catherine Lucey at https://twitter.com/catherine_lucey.