CEDAR RAPIDS, Iowa -- Ignoring her primary challengers, Hillary Rodham Clinton focused instead on the expanding field of Republican contenders as she and her fellow Democrats tried to impress influential party activists in Iowa.
The fundraising face-off for the benefit of the state party came Friday night as the Democratic primary fight - long assumed to be just short of a coronation for Clinton - appeared to be heating up into a slightly more serious contest. In recent weeks, Vermont Sen. Bernie Sanders has risen in the polls and packed arenas with voters eager to hear the message of the self-described socialist who's become Clinton's chief rival.
But rather than confront her most immediate political obstacle in a crucial primary state, Clinton took aim at the other party, vowing to never let Republicans "rip away the progress" made during the Obama administration.
"Trickle-down economics has to be one of the worst ideas of the 1980s," Clinton said, evoking Republican policy from the Reagan era. "It is right up there with New Coke, shoulder pads and big hair."
Singling out former Florida Gov. Jeb Bush, Clinton launched a familiar attack on his statement that Americans need to work longer hours.
"Americans don't need lectures -- they need raises," she said. "So if Republicans really want to help us, why don't they join us in breaking down barriers?"
Clinton additionally pledged an agenda of "small growth, fair growth, and long-term grown," because her campaign "has to be about how we unlock the potential of every American."
Sanders, too, refused to criticize his primary opponent directly. Earlier in the day he edged closer to an attack when he questioned whether Clinton would back the kinds of tough regulations for Wall Street that's become a rallying call for liberal Democrats.
"You'll have to ask Hillary Clinton her views on whether we should break up these large financial institutions," he said during an afternoon appearance in Cedar Rapids.
At the evening forum, Sanders called for a "political revolution" fueled by a "mass movement from coast to coast" that would end the influx of money into politics and take the country off "the path to oligarchy."
"The greed of the billionaire class has got to end and we are going to end it for them," he said. He added: "Please don't think small. Think big."
The Clinton campaign has signaled that it considers Sanders to be a legitimate challenger who will be running for the long haul, noting the $15.2 million he's raised - largely from small donors - in the first three months of the race.
They believe he will find a measure of support in Iowa, where the caucus system typically turns out the most passionate voters, and in New Hampshire, given Sanders' many decades representing neighboring Vermont in Congress. A recent Quinnipiac University poll showed that Sanders has even doubled his support in Iowa since May.
On Friday, Clinton's campaign said it bought $7.7 million worth of television advertising time in early voting states, its first ad buy for the 2016 contest. In Iowa, the campaign paid $3.6 million for time in all eight media markets that serve the state. An additional $4.1 million of airtime was purchased in New Hampshire, which holds the nation's first primary.
Unlike her rivals, Clinton has already built a vast campaign infrastructure, run from a multistory headquarters in New York City, with hundreds of staffers across the country. But so far the Clinton team has resisted any direct engagement with Sanders, fearing such an exchange might alienate the activists and small-dollar donors who will form the base of support in the general election if Clinton should win the nomination.
"You can see that Democrats are united, we are energized, and we are ready to win this election," Clinton said Friday night.
In a fiery address, she slammed the economic policy of former Florida Gov. Jeb Bush, joked that businessman and TV star Donald Trump is "finally a candidate whose hair gets more attention than mine," and criticized Wisconsin Gov. Scott Walker for targeting union power.
"That's why we can't let Republicans take us back," Clinton said. "We're not going back to the Wild West on Wall Street. We're not going back to denying climate change."
Besides Sanders and Clinton, the forum featured former Maryland Gov. Martin O'Malley, former Virginia Sen. Jim Webb and former Rhode Island Gov. Lincoln Chafee.
O'Malley introduced himself as a can-do former chief executive who tackled a series of problems in Maryland by promoting public education, freezing college tuition, passing a "Dream Act" for young immigrants and expanding family leave policies.
But like Sanders, he got some of his biggest applause when he talked about regulating and punishing Wall Street - underscoring the populist mood of the most active Democratic voters.
"Main Street struggles while Wall Street soars," he said. "If a bank is too big to fail, too big to jail and too big to manage, then it's too damn big."
In contrast to O'Malley and Sanders, Chafee and Webb both spoke of foreign policy issues at length.
Chaffee praised the contentious nuclear deal with Iran, exclaiming "What a change!"
"Avoiding war is worth every bit of our energy," the Rhode Island governor added. "This is the right way to make the world safer."
CBS News Digital Journalist Kylie Atwood contributed to this report.