But while Democrats are unified in opposition to the president, they're split over an agenda of their own — particularly when it comes to bringing back working-class, white voters who flocked to Trump in 2016.
After decades of relying on free-market solutions to achieve liberal aims, Democrats have shifted to the left in recent years, and many are calling for more government intervention in the economy. Yet despite the emerging consensus around more progressive policies, it is unclear whether Democrats can form a winning electoral coalition around those ideas, and some say the party must tack to the ideological center.
"People don’t like Trump," Schumer told ABC News. "But they say, ‘What the heck do the Democrats stand for?’ ”
The left has already won many of the important debates within the party — in contrast to past years, when Democrats took a centrist approach to economic policymaking.
President Bill Clinton unraveled crucial elements of the social safety net for very poor Americans when he reformed the welfare system in 1996, replacing it with programs to encourage participation in the labor force. Additionally, Clinton deregulated financial markets and accelerated globalization with the North American Free Trade Agreement.
President Barack Obama also pursued free-trade agreements in office, although without success. The Affordable Care Act, widely known as Obamacare, relied on free-market principles to reduce premiums for individual consumers.
Today, though, Democratic politicians broadly support greater redistribution of income, more generous social insurance and an expanded scope for government — a more ambitious liberalism exemplified by proposals for paid leave and universal child-care benefits.
"Which side are you on?" That is the question for Democrats, writes Mike Konczal, an expert on the financial industry at the progressive Roosevelt Institute, on Vox.
The shift follows a gradual trend among Democratic voters toward more progressive politics. The share of Democrats calling themselves liberal has increased from 27 percent in 2000 to 42 percent today, according to the Pew Research Center. There are now more ordinary people in the party who describe themselves as liberal than who describe themselves as conservative or moderate.
Meanwhile, the distribution of economic resources has become vastly more unequal, and many on the left seem ready for a change. The figures for wealth are particularly striking: The richest 0.1 percent of U.S. households now possess as much as the poorest 90 percent combined.
"What has gone wrong with the American economy isn’t just a short-term flip," said Heather Boushey, an economist and the director of the Washington Center for Equitable Growth. "We’ve had 40 years of economic policies — most importantly tax policies, but other policies as well — that have allowed a small group of people at the top of the income spectrum to garner greater and greater shares of national income."
The victories for progressive Democrats are not limited to economic issues.
The tough-on-crime legislation Clinton signed two decades ago is now widely viewed as a mistake, and Democrats agree on the need for reform in criminal justice. Pro-life Democrats are so rare these days that it was newsworthy when Rep. Nancy Pelosi (D-Calif.) declared that there was still a place for them in the party. Former Democratic presidential candidate Bernie Sanders arguably won the debate over Social Security when he goaded Clinton into promising not to reduce benefits.
Acknowledging that reality, middle-of-the-road Democrats Mark Penn and Andrew Stein urged the party to opt for more moderate positions in an op-ed in the New York Times on Thursday. "The path back to power for the Democratic Party," they wrote, "is unquestionably to move to the center and reject the siren calls of the left, whose policies and ideas have weakened the party."
On the economy, the gist of the Democrats' likely platform in coming elections already seems clear, based on proposals by lawmakers and candidates in recent years.
Many Democrats agree on making college and vocational school more affordable by using federal money to help students with tuition. Another priority is bringing down the cost of parenting. Democrats have proposed guaranteeing paid parental and family leave for all workers, covering some of the cost of child care with federal money and delivering more cash to families via an expanded child tax credit.
Democrats have also supported assisting adults without children by expanding the Earned Income Tax Credit for that group. Meanwhile, lawmakers have called for a massive investment in rebuilding the country's physical infrastructure. Schumer, Sanders and their colleagues in the Senate have proposed dedicating $1 trillion in funds over a decade.
With some exceptions, Democrats have said they will fund these programs through increases in taxes on the rich. They've largely rejected any additions to the national debt, or any hike in taxes for ordinary households.
The worry for Democrats is that Hillary Clinton advocated all of these policies during the campaign, without attracting much interest from the media or from the general public. Trump's unpredictable style as a politician has made it difficult for Democrats to get attention for their ideas.
Compounding the problem is that the same economic issues that do arouse passionate concern among voters seem to be the ones on which the party really does disagree.
For instance, Trump has made it impossible for Democrats to ignore their differences over trade. Those on the left argue that globalization has caused unemployment and dislocation, especially for blue-collar workers. The success of Trump's campaign — in which he repeatedly blamed free trade for voters' economic frustration -- has cowed Democrats who believe that trade is good, on balance, for American households and businesses.
The minimum wage is another point of contention. Democrats broadly agree the national minimum of $7.25 an hour should be hiked, but many are reluctant to say by how much. Economists warn that increasing the minimum wage by too much could make low-income workers too costly for businesses to employ, impoverishing the people the minimum wage is intended to help.
Sanders supported a national minimum wage of $15 an hour during the campaign. Clinton argued for more modest increases.
Finally, on health care, Democrats are divided over whether to modify Obamacare, or to replace the private insurance industry with a single government payer, as Sanders has advocated.
For now, these disagreements are not all that important, as Democrats are united in their opposition to Trump and his agenda. Sanders, as an example, has been traveling around the country holding rallies and making clear his support for Obamacare over the GOP alternative.
Yet as Democrats prepare for the elections in 2018 and beyond, these divisions could make it difficult for them to settle on a simple and straightforward pitch to voters.
Many in the party argue that Democrats do not need a radically different approach on economic issues.
"America’s best hope to remain an economic superpower is an inclusive economy where immigrants start businesses and create jobs, where everyone can make meaningful contributions," Ronald Klain, a senior adviser to Hillary Clinton during the campaign, wrote in The Washington Post. "That message may not have appealed to some working-class voters, but it isn’t condescension — it’s honesty."
Some on the left are looking to Trump for tips. Trump's relentless emphasis on restricting trade and immigration gave him an advantage over Clinton, said Yascha Mounk, a scholar at New America, a research organization in Washington, D.C. By contrast, he argued, the Democratic nominee's appeal to voters was muddled because she had so many different ideas.
"They kept pitching a different policy proposal every week," Mounk said. Instead, he said, Democrats need to settle on one policy with the potential to capture voters' imaginations.
"Whatever the Democrats do in 2018, but even more so whatever they do in 2020, they need some policy that is like that ... one sort of crown jewel that sort of encapsulates what they’re trying to do," Mounk said.
"Message has always been a challenge for Democrats, because it tends to get too convoluted and not very simple," Sen. Jon Tester (D-Mont.) told Politico.
Boushey, the economist, argued that Trump won over voters by convincing them that he could take control of the economy, and that Democrats can do the same.
"That was incredibly powerful -- to say to the American people, the economy isn’t just something that happens," she said. "We have a choice about what kind of economy we want, and it is well within the power of policymakers to enact policies that will create good jobs. We've done it before. We can do it again, so I think whatever we do needs to signal that."
Not everyone on the left shares that optimism.
Lane Kenworthy, a sociologist at the University of California at San Diego, cautioned that while Democrats' proposals would shore up ordinary households's finances and bring down inequality, they might not improve employment and economic growth. Kenworthy suggested that Trump became popular with voters by promising not just more financial resources, but better jobs as well.
"A lot of the stuff that Hillary Clinton was proposing would be really good things that would make people’s lives more secure," Kenworthy said. "The problem is, I don’t think social scientists — at least the ones who study this carefully — have any real good ideas about how to boost economic growth."